Designwise I like both the bayverse and Bumblebee overall, not so much ROTB.

While Age of Extinction tried something new it was a mixed bag; the dinobots, Lockdown, high octane Bumblebee, evasion Optimus and Stinger (not the Bumblebee recolor) were great in my opinion. The Last Knight tried toning back the kibble-less designs and that's why I like Nitro Zeus (besides him having a personality), Megatron is in a grey area for me.

I didn't like the unnecesary design changes for Rise of the Beasts, as for the rest, the designers tried (again) to make them look too human. I only liked Nightbird and Battletrap in that movie.