I also chose to go with the lake, no regrets yet, my kid loves it, birhtday parties don't need to have limits set, invite the whole class - or school, it doesn't matter.
We don't have a heater on ours (except solar) and it heats up just fine, 1.5 weeks ago we were at 80 deg. without the solar panels, up here in Ontario.
But yes, bigger pool, bigger associated costs. It's all relative.