Ummm......help?

I`ll give it an 7 out of ten

I think turtwig/torterra is the best then if you are only allowing between two of the starters. Each of the first three Pokemon you have up there suck really bad, they are bad Pokemon, but you have given them bad moves and bad items. Tip one, just because heracross is fighting/bug doesnt mean only give him fighting and bug moves. Same goes with all pokemon. For Heracross, try a rock type move. Note how rock is super effective on flying, which is heracross' most outstanding weakness. Now if heracross can kill the birds before the birds kill it, thats good. Id suggest something like megahorn, close combat, rock slide and maybe aerial ace/swords dance. Scizor just sucks, forget it. Youve done the same thing to sceptile as heracross. Choose whether you want it to be attacking or special attacking and vary the movesets accordingly.

Your team is awful. They are all horribly terrible except Garchomp who is like 90% good. Get rid of dragon pulse for something like fire fang or brick break and hell do much better. Quit wth focus blast, you like the department store hey? Focus blast is bad.
K ill give you some alternate suggestions for all of them
Torterra- earthquake, wood hammer, crunch(sunny day), synthesis
Gardevoir - blah is sucks, get alakazam or something, gardevoir does not belong on a final team
Medicham - EEEEWWWW really bad get rid of focus blast and focus punch, try and find a psychic move for him, preferably of the attack variety, but either works
Garchomp- see above
Infernape- You are infinitely better if you choose one stat ie choose attack or special attack and role with it, infernape has equal of both. I would suggest straight up switch is for rapidash or arcanine, you already have enough fighting moves and either can rock a flare blitz
Dialga - really really bad. Just do this roar of time, earth power, aura sphere and flash cannon. Simple and effective

Others have said your team is quite good. I agree with them. You Dialga could need some work though. But this really isn't the place to rate teams. Go here: http://forums.supercheats.com/forums.php?forum=1685 and ask. You will get more responces.

As far as the better starter between Turtwig and Chimchar, I will call it a draw and leave it at that. Your Pokemon are not bad, they just have terrible movesets. Use moves that can defend against types that can hurt your team: for example, you can teach Shadow Ball to Gardevoir to repel some ghosts and other psychics. Overall I would give your team a 4.

P.S. A tip on your Scizor...if it has the Technician ability, it will raise the power moves that have a base strength of 60 or less. My Scizor currently has Focus Energy, Rock Smash, Metal Claw, and X-Scissor, and it has given even the most advanced teams considerable trouble. Happy battling!