Garchomp or Steelix?

Hello,
For my Pokemon Platinum team, I am debating between Garchomp and Steelix for my Ground type. I have a Empoleon, Metagross, Infernape, Staraptor, and Luxray. So, Garchomp or Steelix?
Also, could someone give me an honest evaluation of Gardevoir and Alakazam, and which is better, and why?

Garchomp is an Uber/Overused pokemon.
Dragon/Ground
Base Stats:
HP 108
Attack 130
Defense 95
Sp. Attack 80
Sp. Defense 85
Speed 102
Has great movepool and access to Draco Meteor. Evolved from Gabite at lvl. 40
Steelix is a Borderline/Underused pokemon.
Steel/Ground
Base Stats:
HP 75
Attack 85
Defense 200
Sp. Attack 55
Sp. Defense 65
Speed 30
Beastly defense but lacking attack. Has large movepool, but that's it. Evolved by trade (Onix with Metal Coat).
Of the two, I like Steelix (but I'm biased against Hoenn/Sinnoh Pokemon). Chances are, you're looking to crush your opponent before they have a chance. Therefore, choose Garchomp.As for Gardevoir vs. Alakazam, take a look at their Sp. Attack.
Gardevoir: 125
Alakazam: 135
Alakazam is the more popular choice because of that 10 point difference. Also I like Alakazam :D

Interesting. More input, please?

garchomp, simply one of the most powerfull pokes ever made, mix in a choice badn , and a swords dance batton pass, and oh boyo, oponents will wet themself before you (as a matter i've used a 4 boost strategy on my lil chom, and its quite menacing), also it has acceptable defense, alakazam of gardevoir due to him only having 3 weakness, darkness, poison and bug, gardevoir, has a number of lesser resistance, also alakazam, can calm mind, or if you ahve a smearglebatton pass him Cosmic power, clam mind and recover your HP.

Replying to #4

I stopped understanding after "swords dance batton pass". Steelix only has a max Attack stat of 295 if you have a nature that raises Attack, whereas Garchomp can have a max Attack stat of 359 (394 if it's beneficial nature!).
Gardevoir and Alakazam are both pure Psychic, but Gardevoir is more defensively inclined. Unless you're looking at competitive battling, choose the pokemon you think is cooler. I like Alakazam over Gardevoir because of design and power.