Interesting question indeed!!! I am currently running the SD2 setup. Previously I ran the Translator Pro for several years and had the tune NAILED!
The only real reason I switched is because I'm the eternal gadget geek and tweaker!!! I've been running the SD2 for several months now and I'm REAL close on getting this tune NAILED!!
Translator Pro "pros". more tuning features/points to play with.
Translator Pro "cons". more hardware involved....fewer tables to play with....Extender Pro chip required to work to it's highest potential.
SD2 "pros". less hardware (just the chip and powerlogger)....3 full 17x17 tables to tweak (Target AFR, Timing, VE)....extensive tune page.
SD2 "cons". I'm still thinking....
While the Translator Pro is primarilly an exclusive Bob Bailey Engineering project, The SD2 is a collaboration between Bob Bailey, and Eric Marshall (turbo tweak guy) so it is getting the best engineering available by the two major wizards of our community!!!!!!!!
Now, with all that said, keep in mind that both systems are speed density systems, and as such require a good bit of attention and tuning by the operator. A good laptop is a must of course. Even though they are designed to operate with the stock ECM, and are "synthetic"(my words) speed density, they require attention to detail!!!!! like any other SD system. So if one is looking for a plug-n-play solution, speed density will not be your "cup-o-tea".
Any other questions, don't hesitate to ask. There are already a bunch of us running SD2, but very few that have made the switch from Translator Pro to SD2.