I would grab MLB of each since it's free, but I wouldn't really recommend investing in either if you are tight on materials. Saikoro is more likely to see use than Over.on.
Over.on (Armor Form)
Over.on (Armor Form) is an Attacker with nothing notable about it. It's hardest hitting weapon is 5160 POWER with only 1 Range with 10% CRIT DMG Weapon Skill on a 5% CRIT weapon. The 4 Range Weapon has 4560 POWER, with an additional 15% at max range, making it not 5244 POWER at max range, which is nothing to write home about.
It also has terrible Abilities, just the standard 10% ATK for SSR Attackers, and 5% ACC which may as well be an empty slot.
Saikoro Gundam
Saikoro Gundam is mostly a meme MS, being 2x2 sized and a defender that doesn't have Shield Defend. It can be deployed in Atmospheric Maps, so there is that.
It does have access to I-Field Lv2, giving it 40% DR against Beam Ranged, which is one of the strongest Abilities a Defender can have, but again, no Shield Defense so it will only get 40% DR compared to someone with I-Field and Shield getting 60%.
Saikoro has 4 Range, 5472 POWER Weapon with 10% ACC Down, and a 4 Range 3999 POWER Weapon with 30% ATK Down.
