Iron hands get bionics cheaper. They also have Iron fathers who are a cross between techmarines and chaplains, I think.
I know others have advertised already but I'll plug for Dark Angels. The shootiest SM army, they actually get three armies: a normal SM detachment with all choices except veteran squads; a specialist Deathwing which consists entirely of terminators, dreadnoughts and Land Raiders (DA can take one Crusader variant); a specialist Ravenwing which consists entirely of bikes, attack bikes and land speeders (both standard pattern land speeders and/or tornado pattern land speeders can be used in squads up to 3. No typhoon pattern land speeders are allowed in a ravenwing force).
I love the variety in DA. The stubborn rule is an excellent thing for squads led by a deathwing member never have to take a morale check. This means such a squad will fight to the last man. Turn tactical squads into super resiliant speed bumps for enemies assault squads. Swamp said squads with numbers - assuming they aren't already dead from your shooting. You get the option for taking plasma cannons in tactical squads at significant point saving.
I love the DA, I get three armies - all very different. I get to have super-shooty marines. I get to mix heavy weapons and assault weaponary in my terminator squads. The only drawback is less assault options w/ no veteran squads and not the full range of options for command squads. Still get assault marines plus our HQ, terminators and bikes all are very useful in cc. Also `stubborn' units have an advantage over ordinary squads b-c they are much more resiliant refusing ever to break and run..
Hope this helps some. If you are really having trouble deciding why not try first using a vanilla list until you develop a gut feeling for what you want.
Want all sorts of weird rules, strong assault element + ability to field dread as HQ and take a Leman Russ battle tank? Try wolves...
Want the preeminent assault marines with all kinds of charge bonuses + potential extra movement(but involuantry, can be inconvenient for devestators). Want to get a squad of CC monsters for free? Then try Blood Angels and watch everyone cry `cheese' when all you've done is buy the cosex!!
Want assaulty, but religious fanatics led by THE religous fanatic, who take strange scouts in their squads (up to 15 strong!) vows and no devestators? Try Black Templars. These guys get to use as many Crusader pattern Land Raiders as you want..
Want a bit of both with neither the best assaulters nor the best shooters (very good at both, just not so specialised) try Vanilla marines like Ultramarines.
Endrant (thank ghod for that...)