I think your best point cost is the Command squad becasue of the load outs it can have, Plus the special character can greatly improve them as well, and I think Ld is a 9.9 marines, flamer, thunderhammer
LD 9, SV 3+, 18 attacks, 10 wounds
They do okay for an inital attack then get bogged down depending on the rolls, I feel they lack a solid punch. The Thunder hammer is a good hitter but goes last (eh)
chapter champ, 4 honor guard, banner
LD 10, SV 2+, 21 PW attacks, 5 wounds
These guys are nasty in the assault and hold their own, problem is counter power weapons, just pick and choose the fight, and get a transport.
LD 3+, SV 3+, 10 attack, 5 wounds, FnP
FNP makes these guys nasty! plus they have a special character to bolster them (typically) They can have a RB for fire support.
This is what I see with the points being about the same cost. Thoughts?
Also consider Vanguard Vets, equiped with jet packs they have heroic intervention and land where they are needed and assualt when they need to.
Basic Assault Squad with your load out = 225 pts.
Vanguard vet with jump pack and three power weapons = 205 pts x4 pw=220
Well thats my thoughts hope it helps.