Last year, I went to Roys Reeds and to Pomona... if you are interested in only antique advertising & petro... I would certainly recommend Roy Reeds over Pomona.
I walked almost the whole Pomona swap and there was almost no antique advertising for sale. I would not go there with the expectation of finding anything interesting in the petroliana space.
Roy Reed's was neat, but quite small... maybe 20 vendors. You can shop everyone's setup within a half hour... but you will certainly find something to go home with.
hope that helps.
