It depends on what you are wanting to do. I have the 11.5 shocks but can only use certain exhaust. It reduces the lean angle on the right side dramatically. I want to use a set of Bassani road rage 11 but can't with the lowered shocks. 1/2 inch isn't going to do much. I will say that the 12.6 inch stock shocks or 13 inch shocks will give ya a much better ride because of the extended travel.
I went with the Progressive 412 12" shocks and the difference between stock and these are night and day. You have to correctly calculate the increase in seat height using the angle of the shock. Without a ton of math, a 1/2 inch in shock length at 45 degree is about 1/4 inch of seat height. The spring rate and dampening all determine the quality of ride and control of the bike. I have always been more focused on how my bike handles and responds in various conditions and if it looks good doing it all the better. I have seen too many people go solely for the look and when they counted the bike it would not turn, brake, and save the rider. If the bike will not stop, steer, or handle in a tight situation then all the chrome in the world won't help.
To put it mildly I was not impressed with the 440's I put on my FXDB. Figured as long as I had already wasted the money I should do what I should have in the first place. Talked to Howard at Motorcycle Metals and ended up with Ohlins made to order for me and my riding style. The shocks are .5" longer than stock, super comfy and made a huge difference in handling.
My stocks were 13"s, I just replaced mine with 440's. (I am satisfied, the wife is overjoyed). I had a chance to save 10 bucks and go with 13.5's. Even though they may have provided a better ride and not increase the height that much, I stuck with the same 13" that I am comfortable with.
The low end Progressives are not worth it, but the 970's are nice. Otherwise check Works, Ricor, or Ohlins. The extra 1/2" will give you a little bit of height and a little more travel. Probably only 1/4" height like already stated. If you end up getting one of the better shocks, the extra 1/2" won't be needed for a better ride. My FXDX has 13.6" and they are the best Stock shocks made. Ride is much better than a stock FXD. I like it better than my Father-in-laws softail. A lot has to due with the quality of the shocks more than the length though.