If you are using miles, I would concur that the new int'l UA 777's in biz would be better than the other options, since it's a lie flat seat with 15" video screen. However, UA could substitute the older version 777's with the angled biz seat. IMO, AA's 738's in first are not that great.. just normal recliner seats with no leg rests.

If you want to pay cash and try getting an upgrade, I would suggest buying a VX economy or MCS seat and upgrading at T-6 hours. Those seats would be my 2nd choice over UA's (since they are not lie flat seats). Having flown VX SFO-JFK many times in F, VX service is usually a little better than UA's, but not significantly.