Easy to Transform Transformers?

[MummyAbroad]

I remember someone a while back mentioning that some brands of Transformers are so hard to transform that the parents end up having to do it all the time, so can anyone remind me which brand I should/shouldnt get?

My son is 4 and half.

I've bought ds 3.8 V Tech switch and go dino as they look much easier for him to do.

And yes I'm fed up of making and unmaking his car transformer.