I've always found the F chord with the thumb the easy way to do it, both down the bottom and up as high as the 10th.

But the real reason I tend to use it is that, down at the bottom of the neck, when you lift the middle, ring and little fingers off you get neat little notes that come in handy (A,D, and G, I mean). Can't do that so easily with the barre - and can't do it at all if you want to strum a chord with one or more of those notes in it. And you can hammer on and pull off with the thumb, without disturbing the rest of the chord, which would be a lot trickier with the full barre.

If I was playing an F where I wanted to be able to switch to an Fm, I'd probably use a barre... No I wouldn't - I've just tried, and I found I instinctively did it the other way, and it wasn't any quicker doing it with the barre, though I'd have thought it would be.

I think the thing is, it's handy to be able to do it both ways. But using the thumb is definitely my preferred way.

Which doesn't help with my problem playing Bb chords at base position. Now if I could only stretch my thumb over to hold down the A string...