We love the babybjorn potty chair- the bigger one that comes in different colors and has a white insert. The insert is easy to clean and is built up enough in the front that our little boy doesn't make a mess when he pees.
We have a Safety 1rst Potty chair. The positives are: there is a soft cushiony seat which is never cold like a toilet seat can be and it has a cup that is soft so my son never injures himself on a hard plastic cup when sitting down or getting up, it doubles as a step stool so he can stand on it and wash his hands in the sink, it can be taken apart so you just put the seat onto the toilet if your child is comfortable on the toilet, you can use the stool under your child's feet if they do sit on the toilet, it is also quite inexpensive (about $15). The negatives are that if your child has loose stools and uses it on the toilet it can be hard to clean as there are lots of nooks and crannies in it. I don't have any problem since my son is usually quite solid but the few times he hasn't been it has been somewhat difficult to clean. Good luck with your decision.
If I had to do it again, I would go straight to the potty insert seat. The cushy kind that fits right into a regular toilet seat. Skip the pain, skip the mess. You can take it with you anywhere, too, which is a HUGE benefit when training. Same seat here, there & everywhere. If you must get a little potty (sometimes its nice to have one in the car...) get one that is all one piece and super simple. Otherwise, with boys, you can get all kinds of leaks and messes. Good luck!
We have a baby bjorn thing that fits on the regular toilet. My son likes it really well. We also have a little potty chair- just a cheapy. But for boys look for one that has a NON-removable penis guard (or else your son will just continually remove it before or during potty time.
If you want to start him on the big toilet, you can either get a potty seat with handles, or you can always just face him backwards on the regular toilet. He will brace his hands on the seat, so be sure to wash his hands or have those cleaning wipes for hands wit you. That is what we are doing now that he wants to use the toilet in public.
There are also fold-up seat inserts available if you want a travel one to put on the toilets in public.
As for cushy seats or not, my son doesn't mind the hard plastic of the baby bjorn one. And I figured since most toilet seats are hard anyway just get him used to that feeling right away.
P.S. my son mostly uses his little potty chair as a stool to get on the "big potty", but I do find it handy for night time, as we don't have a bathroom upstairs by the bedrooms.