Which ones are "best" is purely subjective :-) I've attached a link that outlines the characteristics of the different species.......C. integrifolia tends to be one of the most available forms but not all selections are entirely 'shrubby'. More like a sprawling groundcover :-) And some actually do extend to some height but lack a vining ability so may be better draped over/grown into a small shrub.

While still a hybrid clematis, 'Harlow Carr' has visible integrifolia parentage and is great if you want a sprawling effect. Extremely long bloom season. 'Rooguchi' is also very popular. And if you can find it, one my faves is Clematis recta 'Purpurea' which is fully herbaceous, forms what I'd consider a very shrubby plant, has purple foliage and produces clouds of small, white fragrant flowers.

Here is a link that might be useful: herbaceous clematis

New Love is a shrub type clematis. It has done very well for me, have grown it about 7 years with a move to a different city almost 5 years ago. Never a problem, it is a nice large shrub in bloom now, seems to handle the drought we are in just fine but it does get shade much of the day. It is well-behaved, does not sucker out of it's area.