Generally say List 1 is better, as they have more guys and you may need number in low points game. However I think itbmay still need a few improvement.
It is better to take more grav guns in biker to make good use of their superior range and number of shots on relentless platform. And it is also better to consolidate Melta weapons (multi melta) on independent Attack Bike squad or Land Speeders as it has much better melta range than melta gun. So don't mix it into regular bike squad.
Don't use biker as assualt units and
imho using veteran sarge with only melta bomb is not good idea. Your White Scars are surely not Ork Nob biker.
You have better
BS and way better range weapon choices. It is better use your mobility to keep distance from enemy fast assualt units. Only Jetbikes can be faster than you
iirc. So you can avoid most combat and just shoot enemy to death, if you want.
If you wnat to use Vanguard Veteran as your answer to close combat, pack one or two storm shield and a few
PF or
TH. Without the storm shield, they are no more survivable than assualt marine but are way more expensive.
Imho, it is better to pack the Landspeeder with either two
MM or just arm it with that missile launcher as backfield support unit.
~Ice~ 