For me (and this might be different for some folks), medium format doesn't have enough adantage over 35mm to warrent bumping up, if you are talking about 35mm digital versus consumer level scanning (flatbed) medium format film. Large format has a significant advantage over 35mm to warrent bumping up and carying extra gear. Any kind of movements you want, large film surface, and ability to develop individual shots separately, not dealing with roll film, and the workflow of a view camera. Me, I just don't really like roll film that much, even if it were 4x5 roll film.
If you are doing 4x5 with a few lenses, the entire setup wouldn't be much heavier than a 35mm setup with extra batteries and fast lenses. Actually, accessories aside, my 4x5 camera with a normal lens mounted weighs less than my 1Ds and any one of 1/2 the lenses I own. Film holders can add a bit of weight/bulk, but that's just part of shooting film. 8x10 and other formats larger than 4x5/5x7 area different story. They can be very cumbersome, but also very enjoyable. I enjoy my 8x10 alot, but I use my 4x5 more often because of it's lack of bulk compared to the 8x10. More than a few 8x10 film holders, and things start to get bulky! So I pick and choose when I bring the 8x10 with me, and when I just bring the 4x5.
I've tried medium format (6x7cm) and although the film size is nice, without drum scanning my results were not really any better (resolution and clarity) than my 35mm digital files. If I were to pony up for drum scans, the results may be quite different, but I don't do that. If I were printing the film traditionally with an enlarger, yes, 6x7 is quite noticeably better than printing 35mm film, in terms of grain, sharpness, tonality, and the size of dust hits. One thing I do like about scanning medium format verus 35mm digital files, is I get the "look" of film, the grain and the smooth transitions of tones. This makes digital camera files look like plastic in comparison. But aside from that, scanning medium format on a flatbed doesn't gain me a whole lot of sharpness and resolution over my 1Ds2 files.
Basically, I think most (not all) medium format setups are kind of like a big 35mm. And for it to be "better" than 35mm in terms of scanning, I think it depends on the route you go for scanning. Flatbed scans of 6x7cm negatives don't seem to please me near as much as 4x5 or 8x10 flatbed scans do. Drumscanned 6x7 negatives would be very nice compared to 35mm digital, if you don't mind paying for the scans, or finding a drumscanner to own.
If you are just looking for a bit more of a film look (grain, and contrast/tones) medium format with a consumer level scanner will most likely get get you what you want, especially if you go for the larger medium format films, 6x6cm or larger. I wouldn't even bother with 645 film unless you have a very good scanner.
If you venture into 4x5, you will probably not like it if you are looking to keep your same shooting style as with your 35mm digital. Large format is much more than just having bigger film, it's a different way of shooting. Even if you are using "fast" and hand held 4x5 cameras like a press camera (speed/crown graphic). I really enjoy it, even when shooting side-by-side with my digital. But it's not for everyone, for sure.