Well, I bit the bullet and ordered a gas powered one over the weekend. I have a bunch of t-poles to set and will also build some more welded pipe fencing, so I thought I'd buy one that claims to be capable of also driving the 2 3/8" pipe posts. I travel quite a bit, so I need to work efficiently when I have time and it makes renting a PITA and not as cost effective. I thought of buying one of the pneumatic pounders like the Rohrer mansaver, but after using one years ago, I didn't think it would be up to the task of driving the 2 3/8" pipe (I used one on t-posts years ago and it worked fine, albeit clunky and not overly powerful)
I ended up buying a Skidril G20D 2-stroke in a three piece kit with a t-post, 2 3/8" and 3" adapter. I chose the 2-stroke over the 4-stroke for a couple of reasons. The 2-stroke was slightly lighter, more powerful and $200 less. Also, when using a quality 2-cycle oil, you get some fuel stabilizing qualities. I've had chainsaws that have sat for extended periods and still fire right up when I pull them out, with some of my 4-strokes, not the same luck.
I looked at the different offerings and decided the Skidril had a great reputation and decent price, compared to the Titan and some other domestic models. I never seriously considered the Chinese knock-offs. I don't need that frustration.
It should arrive next week sometime, apparently they're made to order for the non-commercial customers. I'll give a review when I have a chance to use it.