Well, it depends...
smaller pages load faster. Full stop. For sure a large page will take longer to load so that is not good for you. Also your text to html ratio can influence your seo result.
looking at the different items:
Styles: they should be in separate css files. Gives you better caching and reuse. Has nothing to do with mvc or not. Use the cssfriendly controls for asp.net.
Javascript: same here, use a CDN for stuff like jquery, ajax.net etc. and put your own scripts in one, minimized separate .js file. Not in your page.
viewstate: yes, this can kill performance and it grows fast. Especially on gridviews. You do not always need it and it can be turned off. Use with care... There is a lot to gain here.
Naming of your repeaters, content placeholders etc come back lots of times so keep them small in terms of nr of characters. Will also give you some help.
If you follow this, what is left is your html and the necessary viewstate. if done well there is not always a need for MVC. The size difference will not be that big anymore. Mvc gives you more control and It has other advantages though but the size of your page it should not be your primary motivation. Asp.net 4.5 will add compression and minification so it will be even less important. But the bottom line is that with large volumes every byte counts...