I buy both, I do find some brands got a bit watery and are not nice taste wise when frozen. I use them mostly in stirfrys alot and can't really tell the difference. If I steam them I add some garlic to them, or some lemon pepper or some chilli etc. Shock horror I have even done this to the canned beans that we use camping when I ran short a while ago and had no back up beans in the fridge.
When you are talking about quantity to do a stir fry for a family you could spend $3.98 on a large packet of frozen veg I wouldn't be able to buy the same amount that cost for the variety even at my local fruit and veg shop which has makrs down to 99cents - but I don't fancy a pumpkin and turnip stir fry's
I basically buy a few bags every few months and use them as needed when needed. It is always great to have them in the freezer as back up.