None of those are particularly good learners. I have a good time when I get on one though. Light, quick (surprisingly so) and you can turn them around fast. The suzuki isn't as friendly ergos wise as far as I am concerned to someone over 5'7" as the cr or the yz. the suzuki engine with the powervalve has a friendlier easier to trail ride note to it.
If you have one handy I would say buy some gear and get started.
If you want to look for something in the 4 stroke range that is affordable and reliable the xr200 or crf230, tt225 or 230, or KDX (two stroke that acts like a 4 stroke) are good choices. My feeling is that a 125 4 stroke wont keep you happy as a primary rider for very long, but they are a nice beginning and great keeper should lighter people want to ride with you in the future.
I already am light as it at 130-140lbs.. i actually like the xr200 cant find anything near me