Defense Grid

I ran through the map "Standing Orders" in the 10k resource challenge and, while keeping my tower placement fairly constant, ran through with different types of towers. I made two main kill zones: one at the first platform and one at the center platform. I placed a temporal in each and made sure to spend the full 10k in upgrades evenly amongst the towers (except the temporals). Here are the different combos I tried:

All guns
All cannons

Half guns, half lasers
2/3rds guns, 1/3rd lasers (this makes resources spent equal between the two)
Half cannons, half lasers

Half meteors, half lasers, with a level 2 missile tower
Half concussions, half lasers, with a level 2 missile tower

The results where a little disappointing. Both the all-guns and the all-cannons setups beat the level extremely easily, with no aliens even touching the cores until the last wave with the crashers, who were quickly finished off by the center platform after they grabbed 9 cores.

The gun/laser and cannon/laser hybrids saw no improvement, but generally didn't underperform either. The aliens generally made it the same distance, and the crashers grabbed 9 cores at the end but were killed. In one of the gun hybrids, however, they didn't die until they met the first platform again near the exit (so, underperformed a little I guess).

In the last two experiments with meteors and concussion towers (meant to see if a NON-gun/cannon setup is viable at all) both resulted in cores being lost completely.

I concluded that gun or cannon towers are required in order to win, and that strategies that use them almost exclusively also win. I also concluded that there are probably some situations where a laser tower or two might improve your defense, but that a general rule of thumb is that spamming guns/towers works fine anyway, so why bother.

Do you agree/disagree? Where have you found a laser tower to be a key tower in beating a level or a challenge?

My thoughts are this: lasers need a buff. I read that laser towers have the best DPS/cost in the game, but my opinion is that this is nullified because of shields. If they do double the DPS, but only do damage half the time because of shields, it's a wash. Seeing as the US military has mostly speculated that laser weapons could be used to shoot down missiles and artillery rounds in flight, I think it would make sense to allow lasers in Defense Grid to target flying aliens and gain increased range.

Also, it's your game, but traditionally in other games I've played, "energy shields" are opposite: effective against kinetic weapons but defeated by lasers/emp/etc. Even giving lasers a 50% damage against shielded aliens (on par with the inferno tower) could make them more viable.