this is a common misconception that I have noticed, largely, I guess, do to the overall #'s of available batman 1 vs marvel1...but, in looking at the census, there are 10 copies of Marvel 1,in cgc 6.0 and above...there are only 15 copies of batman 1 in cgc 6.0 and above...so, I would say that yes, Marvel comics is "rarer", but not by as much as some folks think, if we are being grade conscious...
Good point. When I looked at the census I was suprised by the total Batmans (110) vs. Marvel Comics (39). I would have expected more graded Batmans since they are always popping up and less Marvel Comics since they seem much less frequent.