I've got both, although only the McLaren fully tuned.
I've driven the McLaren a ton, and it's easily one of my favourite cars in GT5.
It's extremely agile, fast as hell, and an icon among cars.
The Enzo understeers a lot, it's not nearly as agile, and a lot less "exiting" to drive than the F1.
And I hardly believe the F1 is slower on straight sections. It keeps accelerating for what seems forever.
I even won both
Like The Wind races with my F1, without any extra assists. TCS 1 and ABS 1, that's all.
The F1 can compete among racing cars of a completely different level. Among the cars in the
Like The Wind event, are cars like the Minolta, Sauber C9, Mazda 787B, etc., and while those cars are much better when
you drive them, the F1 is on par with their AI counterparts.
But for a general idea on how cars compare against each other, check out the thread
the best GT5 cars according to stormbringer!.
It's a thorough test of all the greater cars in GT5, and as you can see, the F1 greatly outperforms the Enzo.