In my opinion, TM is actually the easiest one to build yourself just because the parts fit together so well. There's also no need for heat treatments to make parts line up, there are clear lines of where to trim, and we have great build threads from people that know what they're doing.
To get to centurion you then just have to pay some attention to what you're doing and why. Not just rush into things because you saw someone else do it. But it's not actually harder to do, just requires some thought put into it.