Thats reason enough to buy a common size, Is when you have never herd of them. The LTB is one of very few 34" tires unless you count BFG 35's that come out to a tall 33". IMO id stick to the 33-12.50-15, Easier to find a spare and or a matching spare.
All swamper tires come true to size or larger so it will not help or hinder your cause. It will look like tall pizza cutters and the LTB is a softer tire too so you wont see what you will out of the radials if rotated every 3k. To each their own though, Good luck either way
YJ, TJ, XJ, ZJ..... Too many Jeeps!