SPL lab is as close as it gets to a termlab. It uses the same exact motorola sensor as the termlab in nearly replica casing. Never have seen it more than a tenth off from termlabs at events while we're doing parking lot testing (have seen it perform from 130 to 156db). I'm only speaking on behalf of the bluetooth and lcd meter screens.
If you just want to test and get louder, get an spl lab, if you want to get serious about competing and get lots of practice in, get a termlab due to its superior programming for different event setups.