Well, I'll take a stab at why you've been advised that one is more or less for street and the other is more or less for racing.
Although either will work in either situation. Having a MAF will of course be better suited to street use simply because you are able to keep the ECM and car running in closed loop mode. That is to say, the ECM controls engine functions based on feedback from various important sensors like the O2 sensor and the MAF sensor, and calculate/deliver fuel based on the information received. Also with this system, it will be quite easy to get through any smog inspection out there (assuming the other parts are in place) running closed loop control.
With the MAFless system you are of course in open loop all the time. Fuel delivery will be strictly based on what's in table values and not based on measurements being returned to the engine. Sorta like how carburated cars do it, even ECM controlled carburated cars (yes there are such things, I drive one). But a good bit more sophisticated than carburators of course (evne ecm controlled ones).
This type of system naturally requires a much more in depth knowledge of the engine's operating parameters at any given time, usually meaning a laptop should be close at hand with a good in depth scan tool. You'll need to do close monitoring and make the changes accordingly.
It has the potential to be somewhat better during race conditions simply because it flows better. But IMHO, with the LS1 MAF in place you would have to be running incredibly quick (sub mid 10's) to enjoy the benefits of the flow of a mafless system.
Usually by that time you're ready for a FAST or DFI based system anyway.
My recommendation would be, if your car is primarilly street driven with occasional jaunts to the track (like most of us), you'll benifit greatly from a Translator/LS1 type MAF system. Your car will be running in closed loop as it was designed, will benefit from the huge flow increase of the LS1 MAF, and still be a clean burner when required. And with the added benefits of the Extender chip options and features, you'll have a street chip and a race chip all rolled into one. One point though. If you have smog inspections where you are, you'll need to keep a "smog chip" handy to replace the Extender during the test. It has the EGR function removed to make room for features.
