Depends on what you're looking for. FH2 had some standout additions to its list for me, but there were numerous exotics in FH1 that were cut from FH2 if that's your thing, like the Aventador J, Gallardo Superleggera (plus the Spyder as DLC), Sesto Elemento (DLC), and Reventón, as well as the Ferrari 599 GTO (and 599XX), FF, California ('09), FXX, F50 GT, F40 Competizione, and 512 TR (DLC).
On a related note, FH2 on XB360 also removed some engine swap options. One of my favorites in my FH1 garage was a VR6-swapped Beetle. In FH2 you can only turbocharge the original boxer four on the old VWs, which put a damper on my plans for the Typ 2 they added.
Not really. I've never even seen FH2 on XBone in the flesh.
Braking distances are also shorter in FH1 since its tire model has extra grip compared to FM4. However, I've always said it's obvious that FM4 is the foundation for the handling, just with higher limits of traction. I also think FH1 improved on aerodynamics and weight shifting. FH2 on XB360 was probably built from the same engine, but Sumo Digital doubled down on the extra grip and it's practically a full-on arcade racing game (nothing wrong with that, but it was unsatisfying for me after FH1).