If we're going by the pictures you've provided here, it's no contest, because we saw it happen. In that bankai form (not Ichigo's new bankai form, which is not depicted here), he was being demolished by Grimmjow even without the latter's Resurreccion released. It was only because he was using a Hollow mask (which I'd say was a "hollow form") that he was able to defeat him, and then just barely. The highest level he achieved in this bankai form was barely enough to keep up with Ulquiorra, let alone a full-powered Grimmjow.

I think Grimmjow would have won, if Ichigo didn't use his hollow form. But I'm glad, when Ichigo did win, that he kept Grimmjow (barely) alive. :D

Without his hollow, grimmjaw will crush him! Let's face it!

Looking at this match up on paper it seems that Grimjoww would win if Ichigo-kun doesn't use his hollow form.

It has been proven that with shinigami powers, Ichigo is no stronger than number 7. Ignoring circumstances, we've seen the poor guy wailed on by numbers 4, 5, and 6 of the Arrancar, saved on one occasion, and killed on another. Without his vizored abilities, he stands no chance against Arrancar's 1-6, and ten (released) alone. Of course, I'm not sure if he'd even manage to well against 7 and 8 because of their indirect abilities. We've seen many times that Ichigo is extremely flawed when it comes to roundabout techniques that use a certain level a brain power rather than force.

(please excuse my use of numbers; I'm too lazy to spell out the names of the Arrancar right now >.<)

The fact remains that this has already happened and Ichigo got crushed (wishful thinking isn't going to make Ichigo stronger, that goes for the people who voted for him, which I have no idea why). If we say that this could be an isolated battle, then okay, but Ichigo would still lose, because Grimmjow is about as strong as Ichigo Bankai, just in his unreleased form, if not slightly stronger. (At least for pre-Ulquiorra fight anyway, when Ichigo was fighting Ulquiorra with just his Bankai, he was probably equal with Grimmjow in his unreleased form, maybe even a little faster than Grimmjow, as he seemed to be able to read Ulquiorra's movements much better than the first time.)

But, lets face it, Ichigo would still lose to Grimmjow using only his Bankai.

Heh, I like how all the commentators agree on one answer, but the silent majority still votes for Ichigo.

Grimmjow would win. I mean ichigo had a hard time beating him even when he was hollowfied.

Why are people voting for ichigo?

I don't know, I believe it is just wishful thinking - he really has no chance at beating Grimmjow without Hollowfication. Even if Grimmjow didn't use his Resurrecion, I don't think Ichigo would defeat him.

@Whiteflame, I find that funny that none of them have actually given a reason why Ichigo would defeat Grimmjow, on here. Maybe they are choosing just choosing him because they like him more... Liking him isn't going to help him defeat Grimmjow, though, is it?

(Yo, silent voters, please give a reason why Ichigo would beat Grimmjow... I mean, come on, you vote for him, but won't even bother to comment, what's up with that? Maybe you just don't like your chances at arguing your reason with the people who have commented so far, eh, is that it? XD)