I just posted a reply to the same question...
The fly is a OEM type, and the Delta is a race type. You WANT a race type for one simple reason (as you noted) tune ability.
Read this...
http://www.kymcoforum.com/index.php?topic=11219.msg114956#msg114956I have a six year old Delta the has been on three bikes all using different bells, and it is still on the same shoes that came with it. It is BULLET PROOF! But. The stage6 is much more adjustable for fanatical tuning. I like it better than the Malossi but I have much more power than the Malossi is made for.
Ask Louies opinion, and he will guide you in the right direction. He is NOT a profiteer. He IS a scooter racer.
Tell him exactly how you intend to use the bike, and nothing about whatever fantasy ideals you may have. The intended use determines the components. Fantasy use, and we would all have bi turbo / blowers / Nox, and wheelie bars with a switch to give us everyday riding economy.
Give up a few MPG for a few MPH... Fine
Spend a few xtra $$$ for a longer lived part... Fine
Spend several thousand for Loads of MPH, and longer lived parts... Fine
Spend 100.00 bucks, and expect all of the above... Stupid
Your best spent $$$'s will be on the clutch, and then the jug. and then the pipe, and then the carb/intake.
A good clutch makes any bike perform better.