If you are buying a new snowboard, they all have a sticker on the back with the weight specifications. This will tell you which size to get. You can find the weight specs for most older boards if you google. The size of your snowboard depends on your weight and the model of snowboard.
The Burton Feather would be a good choice because it would be more progressive but with a soft flex. A lot of people hate on Burton. I have been happy with my Burton stuff. I never rode any of their boards other than demos. I have 2 Roxy Snowboards, that is a good company to look into.
IT AINT EAZY BEIN STEEZY