The performance difference and thus choice between these 2 boards is pretty close - yet the wind range described is about the whole gamut of most guys shortboarding range(!!) - so to to make any sort of an accuarate/specific informed recommendation, we probably should consider the sail type/s and sizes that you would plan to use ..(most importantly, the sail/s that you will plan to do 80% of your riding on in the new board's ownership as your experience grows)
Depending on agility/balance/determination etc most intermediate 75kg guys can "reasonably" uphaul a 111Lt and this size offers more responsive ride as you progress in higher wind range and choppier water; the extra width (stability) and volume of the 121 does make the task that little bit easier/more practical, but (obviously) the larger board tends to restrict performance/response at the higher ends of the wind/board range (often a "target" area for guys buying a progressive board as they improve their skills/experience).
Construction, well it sounds like this next board would probably benefit from being TuffSkin, which although carrying a mild weight and slightly less crisp ride penalty, certainly wins out in the sort of bumps and dings resistance that you have described. 012 Carve weight penalty in these sizes is usually fairly small, making that "penalty" less of an issue. Also a bonus at the checkout.
BTW, if you haven't seen it & wanted more tech insight ; http://www.star-board.com/2012/products/technology.php
Cheers ~ Ian