The AKG WMS80 and WMS400/450 systems are not cheap. They retail in the $800-900 range ... I'm just talking street price. I've been running 12 channels of WMS80 pretty successfully now ... got most of them for under $200 a
channel (B-stock clearance on some, and used over eBay for the others). If they work, they work. And as long as you take care of them, they will keep working.
The main difference between higher-end wireless systems and "prosumer" systems is the RF front-end of the
receiver. In low-noise areas, with fewer TV stations and other RF equipment, both systems will work very well, and it is often not necessary to buy terribly expensive units. However, in a higher noise environment, such as NYC, LA, Chicagoland,
etc, these lower-end systems will not get nearly the same range as the more expensive units and will be very problematic to use.
That said, if the large consumer electronics companies get their way and start developing unlicensed devices that operate on empty TV channels, many of these lower end wireless mic systems may start to experience noise issues, both from on-channel and off-channel interference, and the interference will be very difficult to
track down. More expensive systems with tight filtering will then be necessary.
Typically, the only difference between transmitters is the amount of
power - which isn't very important. Remember that one must double the
power output to get a +3dB advantage. However, it's often much easier to get this same advantage through better antennas,
coax cable, and splitters. There are other factors such as durability, but you have to go pretty high end to start seeing these differences ($500+ for the
bodypack alone).
Getting the lavs right in my opinion is one of the critical issues ... the move from AKG c417/L (the
stock lav) to Countryman B3 was a very good one. Sound quality, sound pressure levels, moisture resistance, overall durability. I would probably recommend the B3s over all except the
Sennheiser MKE2 or DPA 4061 -- both of which are much, much more expensive. But these three appear to be the theatrical mics of choice for semi-pro or pro theater.
I agree completely here. You're either going to spend a lot of money on very good, reliable mics, or you're going to spend a lot of money replacing your bad mics with more bad mics over and over and over again.