1. Range vs Throughput
We often fall for an advertised router as High Power / Maximum Performance but a router cannot be at the same time serving a client at a long distance and have higher throughput at the same distance. The farther you go away from a router the throughput and signal strength falls. Many routers reviews specify high throughput but mostly at a close distance or even with line of sight which does not happen ideally in our homes. So ideally we should select a router whose throughput does not drop drastically over distance if we have to have a balance between range and throughput.
Also regarding range there is another factor to be considered, the 802.11 (a/b/g/n) is based on the fact that when a packet is transmitted by the router, on receipt the client must send an acknowledgement back to the router completing the transmission cycle hence having higher power routers only mean that their capability to throw their packets is more over a long range but if the client cannot throw the acknowledgement packet over the same distance then the router keeps on transmitting the same packet. So ideally, the dead-sopt in your home that you intended to win by a muscular router could on the contrary be actually improved by making the clients long range with higher gain antennas, etc.
Why High Power Routers Don't Improve Range - SmallNetBuilder
2. Single Band vs Dual Band, the 5GHz dream
While the 5GHz dual band was introduced showing a dream of improving the throughput over wifi specially for media, in reality it still suffers from range being much less than 2.4 GHz. Also the Also lack of compatibility with common N clients which mostly supports 2.4 GHz make 5GHz not widely utilized. I doubt in reality how much is the impact of interference of other near band signals over a 2.4GHz N signal, do not think that to be as much as it is advertised. Rather I would prefer two separate 2.4GHz N routers one to serve for normal clients and another for media / video if at all required (one connected to the other as parent-child or to a main switch)
3. 150 mbps / 300 mbps / 450 mbps
While we sometimes fall for advertised throughput of 150 / 300 / 450 mbps we need to understand that this is achieved using MIMO (Multiple In / Multiple Out) which means that a typical 300 mbps router is trasmitting over two closely placed channels (like channel x ~ 2.412 Ghz and channel y ~ 2.432 GHz) and the 300 mbps throughput would only be achieved between the router and the client only of the client is also capable of transmitting over MIMO (i.e can connect on multiple channels) which unfortunately normal clients do not have usually be it our smart phones, or media player, etc thereby ending up conneting with max 150 mbps. Similarly 450 mbps means transmission over 3 channels simultaneously.
There is another catch in this, there is a concept of channel width typically has values like 10 / 20 / 40 MHz which indicates the number of available channels from which the router can select one or more for transmission. These MIMO concept work only in the 40Mhz channel width setting and most importantly this 40MHz channel width is possible at a closer range only but not at distant locations from the router. Hence even if I have two clients connecting individually at 150mbps link speed with a 300 mbps router it does not signify always that both will get equal benefit of 150 mbps for throughput and might easily end up sharing 150mbps between themselves. This will be the case even if two clients connect to the same router in close range (40 MHz possibility) but they are transmitting over the same channel unless we can ensure that clients are connecting to distinct channels only.
10 quick and easy ways to boost your Wi-Fi | News | TechRadar
3. NAS
Not only my own router but also many newer models support NAS capability enabling USB enabled storage being added to network. But what needs to be kept in mind is that the data transfer throughput is no where near to dedicated NAS (even if it supports USB 3.0), hence becomes bottleneck while sharing bigger media files for streaming like videos. Also once you add a drive, in many cases you will also need to login to the web console of the router and manually mount the drive to enable sharing. So decide and act accordingly on this feature.
4. Other important features I consider to be worth
a. External Antennas
Having external antennas give you the provision to boost the range by adding higher gain / powered antennas later on to boost wifi range which you do not get easily for ones with internal only antennas like mine (Linksys WRT 610N) or even the newest E4200 from Cisco. If you lookup on the net you will see many sites selling E2000 modded with two high gain external antennas and selling at more than the normal price of E2000.
b. Wifi on/off
I see this mostly on Netgear models (I have one WGR614) a nice switch which can turn the radio part on / off keeping all the network switch functions available. This will save router life / power during all those nights when you left the router on to get your downloads ticking on NAS / PC connected wired with router.
c. Dual band on/off
Not seen in any and absense of individual on/off per band makes you login to web console and enable / disable the 2nd band.Some newer router models are offering touch screen control but they come at their own cost.
d. USB Print Server
Some modern ones are giving this feature but beware USB based print servers are buggy and sometime you might have to restart the router / clear print queues in situations where there is an error while printing, my personal experiance using them be it with my NAS or sepoarate USB print server is not that good. Have a dedicated wifi printer now, much better.
5. Custom firmware
DD-WRT and Tomato are two of the most popular custom firmware that are available today freely for flasing your router with. While they offer more flexibility than stock firmware like more control over transmit power, etc but in my case the biggest advantage I found was to that it allowed my 2nd band (5GHz) to transmit another 2.4 GHz signal which the stock cisco firmware did not. Hence now I am running one 2.4 in mixed mode (for G clients) and the other 2.4 in N-only mode (media transfer).
Again in some cases installing custom firmware allows you to use a cheaper router as wireless bridge or repeater.
6. On my radar
Going by feedbacks I am on lookout for importing a refurbised E2000 in and around 30 USD (not willing to spend more at the time) and planning use it a wireless bridge with custom firmware since it can connect at 300 mbps at close range as compared to my existing Dlink DAP 1522 that can connect at 150mbps only.
Another router for long range that I have on my radar is the Buffalo Nfiniti Airstation WZR-HP-G300NH v2 router as I found that to have the best balance between long range and throughput over distance. But again these are future only plans.
7. Comparison of routers
You may refer to this site Real Help For Your Small Network - SmallNetBuilder for comparison of different router models for different aspects that matters most like throughput, signal range, signal drop with distance,etc. Their reviews are very detailed however they do not usually cover comparison measurements in aspects like UPnP scanning / NAS throughput, etc