I think mega steelix is cool, yeah it doesn't have filter but the thing is its so much better offensively in combination with its great bulk, increased weight, and decent typing. With a set of gyro ball/heavy slam, eq, filler, filler, + sand force you get to check so many threats much more reliably in comparison to mega aggron, who relies on coverage moves a bit too much + sometimes isn't strong enough to take out incoming switch ins.
-1 252+ Atk Sand Force Steelix Gyro Ball (150 BP) vs. 4 HP / 0 Def Landorus-T in Sand: 247-292 (77.1 - 91.2%) -- guaranteed 2HKO (choice scarf commonly runs this spread).
252+ Atk Sand Force Steelix Meteor Mash (120 bp-heavy slam due to increased weight) vs. 252 HP / 4 Def Conkeldurr in Sand: 283-334 (68.3 - 80.6%) -- guaranteed 2HKO after sandstorm damage
252+ Atk Sand Force Steelix Gyro Ball (149 BP) vs. 0 HP / 0 Def Keldeo in Sand: 184-217 (56.9 - 67.1%) -- guaranteed 2HKO after sandstorm damage
252+ Atk Sand Force Steelix Gyro Ball (142 BP) vs. 0 HP / 4 Def Landorus in Sand: 351-414 (110 - 129.7%) -- guaranteed OHKO
252+ Atk Sand Force Steelix Gyro Ball (150 BP) vs. 0 HP / 0 Def Gallade (mega gallade) in Sand: 355-418 (128.1 - 150.9%) -- guaranteed OHKO
252+ Atk Sand Force Steelix Gyro Ball (150 BP) vs. 32 HP / 0 Def Raikou in Sand: 216-254 (65.6 - 77.2%) -- guaranteed 2HKO after sandstorm damage and Leftovers recovery
Heavy slam can be used to ohko/2hko slower stuff that are light in terms of weight, and could even use a curse set if there are only physical attackers left. You really don't need to predict that much, as you will be doing so much work against offense and even against bulky offense with the combination of only 2 moves. Obviously you send it in against something that it can check, and easily 2hko the switch in. You can checkmate your opponents that way fairly easily.
mega steelix can be kinda seen in the same way as sand rush-excadrill because it is sorta dependent on sand and because they have the same typing. excadrill would die to have the bulk that steelix has, because excadrill's bulk is kinda meh that it gets 2hkoed by even resisted hits, where Mega steelix is a little more consistent in terms of damage output, and can live super effective hits if it has to thanks to its 230 base defense. you could run sand force on excadrill, but it is way too inconsistent because it would only be much more effective against bulkier teams, and not against offensive ones where it is outsped most of the time, while mega steelix could run a boosting set with curse and beat both archetypes if it has to.
Mega garchomp also has sand force, but its typing leaves it with very little resistances (rock, fire, poison, and immunity to electric), which means that even if it has some bulk too, it will still take a considerable amount of damage from neutral hits, and has to rely on more prediction since both of its stabs are checked by immunities like flying, leviators, and fairies. It is great offensively against bulkier teams as a stallbreaker, but it is worse against more offensive teams that could easily wear it down fast due to lack of good resistances, high powered neutral hits, priority spam, and common coverage moves are run for it. Mega steelix has just as much offensive potential and lays waste to a lot of offensive teams due to sand force gyro ball/ heavy slam + eq stabs, where it can live super effective hits + carries tons of resistances due to steel typing and stop volt switch being a ground type. It has way more switch in opportunities, resulting in more consistent damage output against both team archetypes.
Sand force landorus is more or less in the same boat as excadrill except its slower permanently unless rp, even less resistances, and fares worse against offense, + some walls will even take the coverage moves even at +2 (unless fly hahahhaha).
so lets bring a short comparison chart.
Mega aggron- really good at taking hits better due to filter, can check the threats it needs to check, but fares worse offensively towards overall team archetypes, has to run a stallier set to be viable at times.
excadrill- really good against fast offensive teams, but questionable against bulkier, stallier teams + lack of bulk overall
Mega steelix- really good vs offensive teams, better bulk, really good vs balanced teams, but meh vs stallier ones.
Mega garchomp- really good vs balanced and stallier teams, but fares worse versus offensive teams + lack of good resistances other than immunity to electric.
Sf landorus- good as a balance between a rock polish sweeper and a swords dance stallbreaker, but it really doesn't excel at any of them and has meh bulk, lacks resistances, still hard checked by some stuff even at +2 attack, middilng speed.
Ty for reading :). mega steelix is really cool try it :).
edit: please stop using it as a stealth rock lead pls and ty, you are wasting its potential that way.