<old fart mode>
In the old days decisions like this were somewhat easier because you could visit other studios, and you could even borrow monitors from the local music store and audition them in your studio - by far and away the best test.
So you can't do that anymore, or rather it is a lot more difficult anyway.
I think the best bet these days is to listen to demos and find people who produce music that is similar to what you want to produce. Then ask them what they use. It'll give you a starting point.
</old fart mode>
There are probably some choices that are categorically bad, but it has been my experience that it is far more important that you learn what your monitors do, and learn to work with them.
There are also, most likely, some choices that are better. But the only way to figure this out is to audition different monitors in your space. And the old fart above explained why that has become more difficult<G>. The final choice is dependent on your room and the music you produce... it's just a big fat messy questions<G>!
Some random thoughts...
I would not choose anything with a driver smaller than 6.5 inches, and probably 8 inches. You can get low end from the smaller drivers, but it requires some voodoo, and frankly, no one does that stuff really well yet, you will hear artifacts.
Stay away from anything that claims to magically correct for room problems. Basic physics rules are pretty strict, and you can not solve time domain problems in the frequency domain. Put another way, you can't equalize reflections!
Powered monitors offer a LOT of advantages - the amplifier and driver are well matched, the connection between the amplifier and driver is as short as possible, and you don't need an external amplifier. But there are a couple of disadvantages - if you lose an amplifier channel you lose a monitor. If a more suitable amplifier appears on the market you can't just swap them out.
FWIW, and that's almost nothing, I use a pair of Yorkville YSMs driven by a Crown PS-400 as my near field monitors, and a pair of UREI 809s, driven by a variety of amplifiers, including an old Heathkit stereo tube amp, as mid-field monitors. When the new control room is built these will be built into the walls, and act as mains. As of yet I have not found a sub-woofer that I like.
Believe it or not, these two very different loudspeakers are similar enough, and different enough, to be very helpful.
I also have a pair of Polk Model 5s, and Toa cubes (similar to the old Auratones) that I'll plug in from time to time.
If I didn't have other priorities I'd add a pair of Haffler TRM-8s to the collection, but for now I'm pretty happy with what I have.
The music I record ranges from simple solo guitar to singer/songwriter to horn based pop to orchestral.
Buying monitors is one of the most difficult tasks when building a studio... good luck, and sorry I didn't have a pat answer!