Using IP-based geolocation is possible, but not very accurate. So I suggest you to think about going with a hybrid approach, like trying to get the users location via the HTML5 geolocation API inside the browser and fallback to the serverside if necessary.
I took a look at the two most used geoip/-location modules available for node.js and they both use the datasets provided by MaxMind. AFAIK you have to keep these databases up-2-date manually, which is a clear downer. So you may consider writing a little sync service / script, which updates the database once per month. (More information on MaxMinds free solution can be found here).
kuno/GeoIP is a GeoIP binding, so at it's core it's using the libGeoIP C library, which is okay, but maybe not as portable as the pure JavaScript implementation bluesmoon/node-geoip offers. Both are okay and it's up to you which library you like more. In terms of performance you have to do some benchmakrs (if this topic matters to you) … There is no general answer to the question, which type of module (C-binding/native) will be faster.
If you're willing to spend a few bucks you could also look into MaxMinds Web Service, which is a simple REST API and will be the most precise way to go. The documentation is quite good – so getting started with that won't be a problem.
