I don't recall any of my UT Mclarens has "brake details" (Unless of course the plain silver discs are consider "details").
Anyhoo, I believe the detail level between UT and Maisto Mclaren F1s are fairly close. You won't miss out anything by purchasing either. Also, anything Mclaren F1 is kind of hard to find now. If you can find either in "reasonable" prices, get it! On top of that, There are still some racing Mclaren F1s (Longtails) in 20 to 40 dollars range. They are great alternatives if you can't find the street versions.
Seriously, do you think the chance is high that some diecast model company will release some Mclaren F1 in the future? Especially Mercedes owns 44% of Mclaren right now and Mclaren F1 is essentially the Ultimate BMW.
BTW, Guiloy also make some Mclaren F1s.