Aside from the price/filter factor, you should also decide which kind to get based on how many cats you have and how long are you likely to just leave the cats. That will determine what water holding capacity your drinking fountain needs.
Also, there are two types of drinking fountains. One that looks like a fountain with water falling into a pool, and another that looks like spring, with water bubbling up from under a surface. Sometimes each cat would prefer one kind over another.
I'd like to add you should consider how easy it is to clean. Because you can't imagine the serratia marcescens growth that can accumulate in the running drinking fountain just after 1 week. If ther are too many nooks and crannies, you are going to have a tough time getting to all of them.
If you really want state of the art, there's Pura:http://www.noacare.com/
It comes with RF ID collar tags, and will show how much each cat drank per day through a smart phone APP.
Of course, the downside is expensive.
The first one icon posted is really common here in Taiwan.
There's another brand called drinkwell, which has several models and is also a bit expensive. My cat used one, but I didn't really do that much research when I bought it. If you see a stainless steel drinkwell, it might be worth the price, because of the cleaning factor. However, most drinkwells have expensive filters, and can take a bit to clean.
That brings me to the last option:
Build your own drinking fountain with fish tank supplies.
Yeah, seriously. Most of these drinking fountains uses underwater motor, foam filter, carbon filters and all that stuff used in fish tanks. The parts are actually not all that expensive.
A quick search with 貓 飲水器 DIY would yield a lot of examples.http://flycall.com/bbs/viewthread.php?tid=563946&page=2http://tilttail.blog.fc2.com/blog-entry-3.htmlhttp://cid719779.pixnet.net/blog/post/4 ... 8%80%83%29
I'm tempted to build one of those myself if not for the fact that I am lazy, already bought a drinking fountain, and did I mention I am lazy?
It seems like the key components are:
1x underwater motor
1x tube that gets water away from the motor
1x tube that distributes water to a container
Nx containers of your choosing
1x foam filter
1x carbon-based filter if you want to give extra care to your cats