Yy to sweatiness due to size of norkage 
Baby Bjorn is fine for short periods of time - they are not idea for boys and not great for hips if baby is carried for extended periods of time. For some reasons men seem to like them - I always found ours rather uncomfortable.
Tying a wrap is really easy and I could do it in my sleep - put in on first thing in the morning, popped baby in and out as needed, took it off at bed time.
Just one word of caution: not every baby loves being carried. I had 2 who loved it, 1 who was ok in it and 1 who would only tolerate it if I walked with him, so great for the school run, but not much if you want to do some housework or sit down.