Angle, Saxon and Jute troops are basically the same. Welsh/Briton infantry are fine, I use loads of them. Command your army properly and you'll win if you've picked your battles. Welsh/Briton cavalry are nasty but very expensive. It costs 2000 schillangas to upgrade a light cavalryman to an elite cavalryman.
Welsh/Briton archers are nasty, though, and if you have villages with high relationships with you, you often get the first tier bowman instead of the peasant when you recruit from there.