If you don't want bells and whistles, all you need to worry about is device count. All share the same device database.
Here's the current harmony lineup with MSRP (the full lineup is in the chart link in my signature):
600 b/w lcd, 5 device $50
650 color lcd, 5 device $80
700 color lcd, 6-8 device, rechargeable $120
One touchscreen lcd, 15 device, rechargeable $200
900 touchscreen lcd, 15 device, rechargeable, RF, no macros $350
1100 full touchscreen, 15 device, rechargeable, optional RF, no macros $350
The 200, 300 and Link aren't worthy of consideration. I personally wouldn't consider the 900 or 1100 either based on no macros, but most don't seem to miss them.
Harmony is ok, but I personally think the Xsight Touch is more powerful over all and a much better value.
URC is more expensive and better than Harmony and Xsight over all. They're meant for pro installs, but you can sometimes get the software yourself.
Crestron and RTI are higher end for pro installs only.
Many places seem to be letting their harmony inventories run out, so new models may be on the horizon. But that's pure conjecture on my part. I have no inside info. But historically, new harmony models are always worse than the old ones but tend to look prettier.