Haulmark trailers ok?
another point you'll want to consider is what kind of racing do you do? My jaded opinion is from the fact that my "home" track is two hours away, and any other tracks we towed to were 4-9 hrs away. I also live in the desert southwest which is hell for trailer tires. We were basically putting a new set of tires on our trailer every two years to avoid dealing with failures. The heat was killing them and often when we'd leave town in the "hot" months you could see road temps in the 140-160 range. Our current trailer with the 16" tires has lasted four years and it's nice to see that i'll actually be replacing tires that have wear on them. Not sure of the ply, but the max air psi on the tire is 95. I also carry two spares..... get a slow leak on one tire, and by the time you notice it, the other tire has been overloaded and the chances of it failing is very high..... I've proven this theory.
so if you are in a cooler climate, only traveling less than an hour to one track (and not at 75mph) you probably could use the "base" axles and never have an issue.... but I feel resale would be better with the larger axles.... any aspect with a trailer usually falls back to that "bigger is better" theory.