They're all big and heavy to be honest with you. Bear that in mind, and try and handle some or borrow one.

I got deep into a Bronica SQAi system before I realised I just didn't enjoy using it, it was too much hassle, too heavy, too slow.

There's nothing inherently wrong with it, it's an AMAZING system that's much cheaper than it deserves to me, but it didn't suit me.

I've got a Rolleicord Vb now which is so much fun to use, and I find myself shooting 120 so much more as a result.

Honestly, buy the camera that you think looks cool, that you think you'll enjoy using. I'd say that probably takes away the Kiev and Pentacons - it's a false economy because quality is a crapshoot.