Sorry if this has been asked before, but what sets apart Garchomp and Lando-T as bulky ground types?
For simplicity I'll discuss their bulkier spreads, Tankchomp and Defensive Landorus-T.
Garchomp is better at getting chip damage against physical attackers and can beat stuff like Ferrothorn, Bisharp, and Scizor thanks to Fire Blast, which solidly 2hko's them all. It can phase with Dragon Tail and can more viably run stuff like Endure or Toxic.
Defensive Landorus takes hits a bit better iirc and hits opponents hard with Stone Edge (which it more commonly runs). It has U-Turn, which provides valuable pivoting for balance teams. I think its EQ hits harder as well. Most importantly, it is a Flying-type, which helps it check nearly every Ground-type in OU atm by nature of its excellent Ground/Flying typing. As such, it is an excellent choice against opposing sand teams. I find it easier to fit Landorus onto most teams than Tankchomp.
I think that both are good, but it takes analysis of the rest of your team's pokemon to figure out what you need to be checked/countered. That should help you decide which to use.
Additionally, Hippowdon is nice since most Electrics can't 2hko it with their coverage moves, it gets reliable recovery, and it can set sand. However, it is certainly more passive than the other two.