Lots of different veiws on this. I would run more then one filter for insurance. If you plan on having lots of tanks in the 100 to 200g range, it would be a good idea to have the same filters on all. Myself I use the XP3 it suits my needs well, the ehiem 2217 would be another good choice.
As for a single filter, a W/D sump would be hard to beat.
As for a single filter, a W/D sump would be hard to beat.