Not bad, the 1st list looks like more
TAC, maybe able to win the game in a War of attrition way, the 2nd one looks more like a all or nothing.
If facing those top tier
OP army, I think I might choose 2nd list for its alpha strike potential. You are might face a army that can dish out 100+ S6 shots plus possibly D templates all on super mobil platforms. Your 15 space marines will not be able to hold for more than 2 rounds of shooting. You will eventually get piecemeal before you could grab enough maelstorm objective points, especially if you draws "kill a unit" type mission and found that all what you are able to shoot at is WK and Warp Spiders who are next tolarge
LOS blocking terrain, plus your Centurion Star is now being tied up by 5 Striking Scorpions with Klaw Exarch. In such view, launching an overwhleming alpha strike may be your only chance of winning. Although you still need to pray that everything goes just as planned.
Besides, I have a few idea for your 1st list. It looks like 15 Tactical Marines are not enough, I suggest if you want Tactical Squads to win the War of attrition, take At Least 30 of them and load them in Droppod or Rhinos. A friend of mine has such a play style you might make reference if you want: he runs 4+ Tactical Squads in Rhinos, all 10men with melta gun, 3+ 10men Scouts (by 10th Company formation), some take Snipers some takes
BP and
CCW,
HQ being Sergeant Telion, and one IK Gallent. If there are points left, then he takes either a Vindicator to attract fire or some assault squads, every Sergeant take a meltabomb. This simple but very efficient army combined with his playing skills had defeated many
OP army, including my Necron, Ironhand Smashfucker; my other friends' Jetseer+Archon shadow field+WK Eldar ally army, and a Flyrant spam army.
Anyway good luck in the Tournament