Alright I'm 5 foot 8 and 135 lbs when I wake up. I have pretty alright sized hands but still small. I use one pair of Title 14 oz training gloves. I'm taking boxing more seriously and plan on competing this year or early next year. I already got a pair of sparring gloves from Rival and plan on getting some bag gloves too. I'm looking at the Rival Elite Bag Gloves which are 70$ (and as far as the reviews go, is an epic price!) I've seen somewhere that for sparring/mitts I should use 14-16 oz and for heavy bag I should go lighter. Should I get 12 oz for the bag or 14?
I prefer 12 ounce for someone your size when I was training fighters (amateurs and a few pros). You want to be able to learn to strike the bag for impact and snap and that's probably easier to learn with gloves that size if you're below, say, middleweight. Just an opinion. Also, I still stay around the game a bit (my brother is involved) and I've seen the Rival products and I really like them.
I think its good to try different sizes. If you have a problem dropping your hands maybe should stick with the heavier gloves. If you are working on speed and combos maybe stick with the smaller gloves. My hands are all jacked up and prefer the gloves with the most padding which happens to be the heavier kind.