Nobody can tell you if a 21" monitor will be too big for you. Personally, I like a 17-19 more than a 21, but there's plenty of people on here who like their 21's. Probably some that would take a 42" if they could get it, too.
Find one to try out. This question is up to you, not us.
i have a 21" viewsonic and i do love it, but its not without problems. if i didnt have an L shaped desk, my monitor probably wouldnt have fit anywhere, and it also weights almost 70lbs. don't get me wrong tho, i'm really happy with the purchase.
auburn9698 is right tho, see if you can use one somewhere for a while to see if you feel that a little more screen size is worth the extra money, space and weight.
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