Well, I've currently got an ICS MP5SD2 enroute to me from 007. Ken personally recommended it and all the reviews I could find on ICS MP5s made it a favourable choice. So that's clearly what I'm leaning towards.
Ofcourse, there is still CA and TM which make good solid MP5s. TM may have a plastic body, but it's internals are golden and from the more recent reviews of CA that I've read their quality control seems to have become alot better. In the end it's up to you, read reviews and form your own opinion and go from there. Google is your friend (and so is Arnies). Ultimately, the best way to get a good idea of what to spend all your money on is to get out to a game if you can and see what everyone is running, maybe pull a few triggers, find out what floats your boat.
Oh and unless you're left handed there is really no advantage to the ambidexterous Navy Trigger group over the right-handed SEF trigger group (and the SEF trigger group is supposed to have better 'clicks' than the Navy trigger group). That's the only difference between an SD2 and an SD5 (airsoft wise).
Out of Sport. Have Fun!