Both types of Bears can be very effective, but both have their problems. Of course the problem would be immunities to their said damage type. Either way, it's not incredibly hard to have a weapon switch that could fix that problem.
Mauler's are more item dependent and Fire Claws Bears are skill dependent. If you were going to be a FCB, you would obviously want to focus more on synergies than other things. You wouldn't really want a Spirit, and you wouldn't want more than one point into Werebear. The reason is because +%ED does nothing for this character because you are relying on Non-Physical Damage, and just attacking at the fastest rate possible. Also you wouldn't need HoW for AR either, because you would have more than enough AR with Fire Claws. So instead you would want to focus those points into Synergies instead. You could max 3 Synergies to Fire Claws, Fire Claws, and Lycanthropy. If you need more information on a Fire Claws Bear, I would suggest you take a look at the FCB Guide by Coldarmy. It is for PvP, but the information still carries over to PvM.
Mauler's are more item dependent, and you really want to rely on a big fast 2-Handed Weapon. The possiblities vary upon your funds, and if you're well off, then the possibilities are near endless. If you lack a lot of funds, there are some cheap weapons that are very good. IK Maul, Ribcracker, Buriza, Reaver, Bonehew, the possibliites are close to endless even for the person without the funds. Of course if you had the funds, you could get into some pretty crazy cruels of quickness, and BoTD's. The weapon is probably the biggest factor in a Mauler and how effective he is. Skills look ok, you'd have an extra skill you could max, so that leaves the possibilities to be huge. What I would suggest is that you do put a point in Hunger, because this skill is an incredible life saver. You could also get by with less points in Shockwave if you have a good amount of +Skills. You can check out TheDragoon's Werebear guide, it's not completely updated for 1.10, but it is still very helpful.
Or you could combine the two into a Hybrid Mauler Fire Claws Bear. Here you could drop the HoW and max Firestorm for a Synergy. Then you could also equip him with Stone Armor for a free level 16 Synergy. It's a best of both worlds build, but you lack some in terms of Fire Claws damage. Of course if you had the funds, you could get 12k+ Maul and 5.5k+ Fire Claws. That's close to a perfect build though.
Any way you look at it, Bears will be incredible. Shockwave IS the best PvM skill. Once you get it down, you shouldn't have a problem really with any of these builds. Which one you use, is up to you.
