Agree and disagree.
My first charcoal grill was my OTS. I alsways said that was all I needed. I always said that the ash pan and hinged grates were overrated. Then last year, I bought a Performer off of CL and I LOVE the ashpan and hinged grates. Hell, I even went and bought a hinged grate from Home Depot for $18 for my OTS.
The hinged grates are a HUGE advantage on longer cooks on the kettle for adding coals without having to remove the entire cooking grate from the grill. The ashpan is great for keeping the wind from blowing ash all over the place. PLUS....the hot ember on the foot thing is SOOOOO true. It holds ash for several cooks, so you don't have to empty every time.
I don't see a difference in "ventability" between the OTS and OTG, though. The only difference is the handle, but the vents in the bottom of the kettle are the same.
Anyway.....I'd say it's worth it. If you buy a OTS and then buy a hinged grate and mod the ashpan, you're nearly there anyway, money-wise.
Have you checked CL? Rare, but I've seen plenty on there.