Resolution is a wonderfully easy number to point to which probably has a lot to do with why we hear so much about it; heck even our cellphones seem to be in a race for the highest resolution. More resolution obviously means more detail and what could be wrong with that? The problem as with so many things is that there is usually an engineering compromise that had to be made to get you that extra detail which ironically you might not even be in a position to take advantage of even if you needed it which even more ironically you probably don't.
The first thing we should probably talk about is common usage. Where are your photos going? Are they being printed? How big?
If we assume these photos are going to be used on the web then almost everyone these days with a relatively modern computer is going to be using an HD monitor and since its probably going to be on Facebook or some other web based viewing portal then we can assume you probably wont even be seeing it full screen. So heres the thing. An HD monitor is about 2 megapixels. That's right. Two. Assuming you've got your photo up full screen and that there are no borders, ads, or text describing the photo anywhere you'll be working with two megapixels. Realistically you'll probably be working with less than a single megapixel.
Ok lets assume the photos are going to be printed at 300dpi which has traditionally been what we use. I'm just going to list this one out. Keep in mind that the larger the photo is the farther you typically stand from it and the lower the resolution actually needs to be. Billboards for example are often only printed at 6-12dpi.
3.5x5 = 1.5mp
4x6 = 2.16mp
5x7 = 3.15mp
8x10 = 7.2mp
13x19=22.23mp - The larger home printers will do these and I used to print using a 12mp camera with excellent results.
24x36=77.76mp - I've seen numerous well done prints done with cameras as low resolution as 16mp. Remember this is pretty big and you'll likely be several feet back from it.
With larger prints it's fun to have a higher resolution camera because when you get close you can see all sorts of fantastic details. I've made a print of the Las Vegas strip 15 feet wide which was composed of 17 different photos from a 50mp camera that is so detailed you can just make out the insides of some of the rooms but having said that nobody that I know of has ever noticed without being told. The proper viewing distance of that print is at least 15 or 20 feet and I probably could have achieved the same overall effect with a fraction of the resolution and honestly I'm not sure anyone will really ever notice except me. Having said all of that in that case I added some complexity to the shoot which in turn added complexity to the editing I didn't give anything major up other than time and I'd do it all over again. To take that same camera to a poorly lit event would hurt the photos rather than adding a touch of magic.
I mentioned earlier that even if you have a super high resolution camera that you might not be able to take advantage of it. the great irony is only the best lenses are capable of resolving what even low end cameras are outputting these days. You need to have the very best lenses around to resolve the higher density sensors.