@MachGO, i agree with points 4, 5, and 6, but i think that points 1-3 arent correct at all. roys SHFFL is not slightly better than marths, its MUCH better than marths. roy can actually utilize full hops >falling fairs/nairs as a baiting and punishing technique. marth can only use those hardly as a defensive technique. normally a marth putting out full hops is asking to get punished, but thats not the case with roy, as he has a very good SHFFL.
for point 2, marths grab range is SLIGHTLY longer, but that doesnt really take too much away, and honestly, their throws lend them to pretty similar stuff. sure marth can dthrow >tipper fsmash unlike roy, but roy can very easily use several of his throws and DACUS into them, lending him very comparable damage output. theyre actually a little TOO similar to marths. and the only real difference is the increased KB on uthrow.
point 3 is perhaps the one i agree with the least, as i think that roy is a far more mobile character than marth. idk the exact stats, but even if roys WD and run speed are slightly (and its definitely slightly) shorter and slower than marths, his overall aerial mobility far surpasses marths. his fall speed allows him to cover much more space in a shorter amount of time than marth can, and it lends to a much more significant increase in mobility than the decreases caused by slight stat differences on the ground
in regards to spacing, i honestly think that marths benefit from tips actually doesnt play as huge of a role as it may seem. roy actually does benefit from tips, the difference is that he gets combos out of it. additionally, roy has ftilt, which either has the same range as marths fsmash, or could honestly be slightly longer. regardless of its actual length, its an amazing spacing tool, one of the best in the game actually, and it sets straight up into tech chases on fastfallers.
overall, i think when talking about marth and roy, its going to boil down to recovery, and efficient kills. marth has his very effective ken combo, and also has a very effective offstage edgeguarding game. roy is very difficult to use offstage, and does not have an efficient, bread and butter, low percent destroyer combo like the classic fair > dair. so in some MUs, marth may excell at getting quick and efficient kills, while in others, roy might excell because of his longer combo strings, and greater variety of kill combos. also, there are certain MUs where roys worse recovery and susceptibility to combos will hinder him much more than normal as well. because of his great mobility and fast, ranged attacks, however, i would expect that in most cases, roy would perform like falco, in that despite the fact that his recovery is bad, an amazing onstage game would prevent him from getting in sticky situations too often. just when those certain MUs come along where he can be exploited very easily, it would be detrimental. looking at the big picture, i think that roy does have a lot of potential to out-perform marth, its just MU dependent, and across the board, its going to come down to if roys onstage game can pull the falco effect and be enough to get past his horrible recovery.