Don't know who decided to move this thread.... Was just fine in commercial tree care and climbing.
Harnesses are such a personal thing. You really cant say which is 'best' since it depends so much on the feel of wearing it. I'd say that goes double for sit style harnesses. I've tried a few, and never really found one that was comfortable. Some of them really do squish your nads, which negates the comfort factor of the seat.
In general, it's true to say that leg loop style harnesses favor more mobility and greater freedom and lighter climbers while seat style harnesses favor longer sit times and fat bastards. Within each class there's a lot of distinctions to be made though. There are leg loop harnesses that offer a lot of mobility and comfort even on long freehanging ascents for fat bastards - treemotion, and buckingham ergovation come to mind. While there are also seat style harnesses that suit lighter climbers.
I favor a leg loop style harness with a floating D for the greatest range of movement. I use the treemotion though I'm really too large for it. It's still comfortable with my 245lbs up in the tree. You don't want to be hanging there all day though. You can always use a bosuns seat together with a leg style harness on the odd ocassion that you need to hang around a long time. I've done it during industrial access.
It seems hard to justify spending $$$ on a harness, but your life and daily comfort is worth a lot. Even if you rate your harness for only 3 years (you'll likely use it a lot longer than that!) then even a top shelf harness is worth less than $1/day. Small price to pay for your life and comfort. A good harness and good set of spikes is a great place to start
Shaun