Mats: the Martelli as they seem to last much longer are are gentler on your rotary blade. Well worth it. I do have 2 very large mats that I store under my bed for squaring up quilts. These aren't Martelli as I don't use them enough to find them cost effective.
Rotary cutters: depends on what fits you best. Many of my friends love the Martelli ergonomic rotary cutters. I can't use them because I would need finger pressure I don't have. Borrow from friends and try the out. I love Fiskars pistol grip cutters and the Olfa squeeze grip cutters where the blade goes back in when you aren't using them [the absolute best for working in a class or with others, no accidents waiting to happen.] Basically, whatever you bond with and can work effectively with.
ali