The main thing to consider is what sort of use will you be putting the phone through.
I have an HTC One and it has a phenomenal screen, so if you are wanting to look at pictures or videos, that is a great one to get. If you are just looking for a mid-level phone which won't cost the earth to buy, then many of the manufacturers can help. All the mainstream manufacturers (Samsung, HTC, Sony, Motorola etc) have a number of really good mid level phones that can offer great performance for the average user at a lower cost.
Maybe ask yourself a few questions, like:
1) Do I want great battery life or just average?
2) Huge screen with high pixel resolution?
3) Are the built in apps/functions worth it (such as Near Field Communication (NFC)) ?
4) Do you want a 4G LTE handset?
Obviously there are many more questions you could ask. If you haven't already registered on here, we have many forums dedicated to the various handsets. There's pretty much one forums for every handset on the market, except the obscure ones (and even some of those!) It's well worth a look about and if you're doing research, I think it will prove very helpful to register and check things out. It's exactly what I did when I was swapping my phone a while back.
If you are looking at getting a cutting edge phone, there are plenty on the market at the moment and a good few more about to hit the shelves. The Samsung Galaxy S4, Sony Xperia Z and HTC One are all great phones but their prices are marked at the high end of the market. All three of those manufacturers have their next tier of phones about to be released too, such as the Samsung Galaxy Note 3 and S4 Mega/Mini, HTC One Max/Mini and the Sony Xperia Z Ultra.
Happy hunting!