Also, look at it from a realistic point of view...
In the SE clockwise through NW sector, there is virtually nothing but ocean, and a bit of the city of Key West. The 1500' MSA makes perfect sense.
OTOH, in the NE sector, there is little but a few other keys and a bridge/causeway, EXCEPT a tethered balloon on Cudjoe Key that goes up to 14,000' or so. Therefore, the 15,000' MSA.
Also, the magnetic bearing from a VOR would overlie the radial, so there is no practical difference.
I would prefer that the MSA depiction show the outbound radial instead of an inbound bearing. However, since the depiction is on an approach chart, many people may tend to mentally place themselves with regard to inbound course/bearings. Hence (I assume) the use of the inbound bearing.