I am a proud owner of Blake, I wear mine very often. I bought a black Stam from Nordstrom a while ago but ended up returning it, that's just me though. I love bags in cream, Stam is available in White Chiffon and Blake comes in Tapioca this season.
Weigh and style vary from person to person. My good friend uses her Blush Stam very often, she doesn't think her fully loaded Stam & Paddy are heavy. She's known for loading up her bags though. =)
I would recommend trying both Stam and Blake at your local store, go with what you are comfortable with. You can also test them out at home before deciding. Good luck. =)