Lecram said:
I think doing it either way is a valid way of doing it. I agree that it does change the FEEL of certain weapons depending on how you do it.
It's not just the feel, it changes the whole metagame.
Choosing your weapon is a game of risk vs reward. The actual probabilities are pretty complex to calculate due to amount of variables, but the trends are pretty intuitive and boil down to using the heaviest stuff on heaviest and slowest enemies, peppering frail but nimble enemies with hail after hail of light gunfire, and finding an approximate golden mean for more balanced enemies. Another way to view it would be, against any particular enemy, you always want the lightest, fastest weapon capable of doing significant damage to him. This is, for example, why Astartes master all sorts of weaponry and why it makes them so dangerous - potentially, their diverse training and vast armories allow them to engage all kinds of enemies in the most optimal manner.
Now, if each Dodge roll becomes contested, the whole "choose your weapon wisely" minigame goes down the crapper, because suddenly the most heavy-hitting single shot weapons also have the best chance of connecting, and thus become king of the hill against all sorts of enemies. Just grab a Lascannon and a Melta Pistol as your sidearm and you can go to town. Same with the melee weapons - say hello to your friend Power Fist, you're going to spend a lot of time together.
All in all, making Dodge rolls against single attacks contested would be a great step towards the One True Build, and that's always a bad thing.