Imo both are extremely stale builds, the gmauler probably more so, as once you use your spec you have 0 KO potential... I would go with an obby mauler (you can always transition this into a gmauler if you're so inclined, but I would recommend 60 attack which isn't that big of a cmb difference but opens up a lot more combo possiblities) or an obby tank - I hear those are a really fun build (albeit a much bigger time investment).
Depends on what you like, obby maul if you enjoy 1 hitting people, gmauler imo is more fun in general, high range+mage with gmaul is the way to go i think
i feel like obby mauler is so boring, and boring to train. the gmaul you can get nice KO's and better PK's, but it's more training. if it was me - i would do the mauler. goodluck!
If you get 55 slayer on the obby mauler you can use the slayer staff and that's a good way for an obby mauler. Other than that I would have to say a gmauler because they can be fun to use at times.
But in my personal opinion, I would prefer to use a 60 attack pure with dragon scimitar and dds. You could also try a range with void as those are fun to use as well if you have the time to get the stats and void that is!
gmaulers are more common imo. Also, you may want to just make it a 60 attack pure, so that it can use a dds/gmaul spec combo. obby maulers are alright, but they're no fun imo. They hit high, but so infrequently that it's frustrating.