My Sigma lens isn't as sharp as my Tamron lens or my Nikon lenses. Mine is an 18-250mm. I get okay results but I wish it were sharper.
Hmm... to answer the original question, which would you use more? Which would you ENJOY more? Our laptop is really old (like 6 years, I think) so I'd probably want to upgrade it before I could justify a lens but if you are going to be taking tons of pictures with that lens it could well be worth the trade off.
