As the others have said, no speed difference for you if you go for 'Unlimited Infinity 1'.
I think 'basic' Infinity 1 has a throttle on p2p still, and also a usage limit.
Infinity 1 gives 2GB in BT Cloud rather than 50GB on Infinity 2.
BT Cloud isn't ready as a serious solution to anything yet, so I wouldn't pay extra for that.
Moved (with trepidation turned relief) to BT Infinity 2 for upload speed. Happy BE user for several years.