From my understanding, the Gen 4 evos and prevos are somewhat controversial. I personally generally don't like them, for one big reason. It's not that the designs are bad, but rather that the designs don't mesh well with their pre-existing family members.
The clearest example to demonstrate this is Mamoswine.
Mamoswine's fur is a different shade of brown, its eyes and legs are visible at all times, and its nose is a different shade of pink and is triangular instead of circular.
There are other offenders, too. Roserade's roses are blobs while Roselia's roses are detailed. Mime Jr. and Chingling have very different color schemes than Mr. Mime and Chimecho. Rhyperior is also a very different color than Rhydon and Rhyhorn, but that's sort of justified in-universe by it bonding with the Protector.
To be clear, I like most of the designs in isolation (Roserade in particular is super cool looking), but when placed next to their family members, it becomes VERY apparent that these Pokemon were not designed at the same time.