PC V w/Auto-tune gives you wide band capability like the ThunderMax but, unlike the ThunderMax, it doesn't replace the ECU so basically you'll need to shove a PC V and Auto-tune module under your seat. Not always hard, but I'm just not a fan of more wires and modules stuffed in there. From the units you mentioned, here's what I'd do in order:
(1) ThunderMax w/Auto-tune ($800)
(2) PC V ($360) + Auto-tune kit ($370 = $730 total)
(3) TFI Techlusion ($260; its a blunt instrument, compared to the above)
Click to see Nightrider's suggestions. He doesn't even mention the PowerCommander but he wrote the page in the PC III days, so I'm not sure if he likes it or not.
The Daytona TwinTec is similar to the ThunderMax, with smaller wire connections. The ThunderMax is arguably more popular and arguably the greatest support overall.
I have the SERT. It actually reprograms the Delphi ECU which I'm a fan of. But, yes, you always have to have the dealer do it unless you order the software and cables (which isn't that expensive but it's complicated). Personally, I would not recommend the PC III as it forces you to remove your O2 sensors but your bike doesn't really need them... just a lot of people have noticed lost fuel mileage and I've heard of issues where the PC III has fried the stock ECU (I don't believe that, though). Also take a look at the V&H Fuel Pack. I've never heard of complaints about this unit when you have V&H pipes.
