Aren't the Foundry ones small? I thought the 7th Cav figs were the same size as their old townsfolk range which is definately on the small side.
No. Foundry figures are a bit better fed than the Artizan, and there's some thicker detail on some items which can be easier to paint. The advantage Artizan has is that the saddle and horse furniture is cast on the horse, while Foundry casts it as part of the rider. The two lines will mix well, especially in a skirmish game, as long as you use the same painting style.