4a,
Your question is like the proverbal "which oil is best" question. You'll get a myriad of responses here.
I have the exact same tire size as you do, I went with The Hercules Power STR, radials, in Load Range D, only $3 more per tire!
I like them a lot, and I'm sure they will last me a LONG time.
Regardless of what brand you choose:
1) before you go on any trips, inflate them COLD to the maximum stated sidewall pressure.
2) Be VERY careful not to wack any curbs or big pot holes with them if possible.
3) Keep them covered and park on wood planks when your storing the trailer between camping trips
4) Most trailer tires are speed rated to 65mph! Do not exceed that for any extended period of time or you will overheat and weaken your new tires and they will eventually fail.
This is just my .02 for what it's worth. There will be some difference of opinion on some of my points, and that's OK, it's just what works for me.
Good luck!