Point 1 is quite clear - that is the MVC format as delivery by your Sony TD10 delivers today. No issue to import and edit that in Vegas.
Point 3 is the progressive Format in MVC 1080 24p that should make a difference - I have no sample yet, but I think that this can be imported in both Vegas and PD10 too without an issue. Hopefully.
Point 2 is a new format - stored as interlaced format but without a time difference between two i-frames. So two half frames shoot at the same point in time. So it is not really a progressive format, but has two half frames. I have a first sample here from the PAL version, what is 1080 25p * - it is also MVC and this format can be imported in Vegas, but shows a black preview screen. It can also be imported in PD10, but the PD10 tends to crash with that format. So this is something new, and frankly spoken: I do not see the added value by this 1080 30p/25p really - since the camcorder has 1080 24p anyway. I see no benefit from that footage, not yet at least.