It's tough to know all of the differences since the full specs haven't been released and no one has tested it yet, but most improvements are with regard to picture quality rather than any functional differences (such as more ports, etc).
The main improvements/differences in the S2 over the S1 and the V25 over the V10 are:
- lower list price (For the S2 it is $2,799 vs $3,199 for the S1. The VT25 is $3,999 and although this makes the VT25 only about 43% more expensive at list, the highest end Panasonics always get discounted a lot less than the next highest and this should make the difference in street price about 60% more for the VT25 than the S2 )
- improved black levels, colour and contrast (For the S2 it's 2,000,000:1 vs 40,000:1 for the S1 and for the VT25 it's even better)
- lower power consumption (EDIT June 23, 2010: On-Mode Average Power Consumption of the S2 is 214 watts, while the S1 is 365 watts, so the S2 uses 59% of the power of the S1. You would save $30/year if electricity costs you 10 cents/KwH and you used it 5 hours/day every day)
- lighter (the S2/S1 weights are 136.7lbs/145.6lbs with stand, 123.5lbs/132.3 without stand so the S2 is 8.9 lbs lighter than the S1 with stand and 8.8 lbs lighter than the S1 without stand)
- no S-video on the S2 (they used to have it on the S1, but then you only get an SD picture with S-video input)
- no PC or RS232 input on the S1 or S2 but they have it on the V25 (makes no difference if you don't want to hook up your PC to the TV)
- no 3-D capability, TXH mode or 24P cinematic playback mode on the S1 or S2, but the VT25 has it.
- more tweakability of settings in the service menu of the VT25 than on the S2 (and it is suggested that only a professional calibrator should touch those settings unless you are very careful and know what you are doing). I think the S2 has the same settings as the S1.
- the bezel is slightly different on the S2, but the 65" (and 58" for that matter) S2 does not have the 'clean touch' bezel that the 54" and smaller S2 sizes have.
The main reasons to go with the VT25 are for the 3-D capability, THX mode and/or 24P cinematic playback. If you want any, some or all of these features then you have no choice but to go with the VT25 series. If you are not interested in THX mode, 3-D or 24p cinematic playback then you are left with the decision of whether the (possibly) improved contrast, colour and blacks (but we won't really know this until the tests are in) are worth paying the 60% premium over the S2. You be happy to know that many calibrators have noted that they can get quite close to making the pictures on the P65S1 and P65V10 look very similar, albeit not the same, but who knows if this will be the same with the new models, S2 and VT25. But, remember, when you have the set in your home, you have no reference point (ie the set you did not buy) with which to compare and you will probably be very happy with either set.
One other consideration that should be noted is that a lot of people will look to others on here to guide them on whether to go with the S2 or the VT25 set, but, other than the empirical differences (some of which can be measured by test equipment, but possibly not perceived depending on the pair of eyes you were given and on how your brain processes the visual information) much of it is subjective. What is bothersome to some is not to others. What looks better to some looks only marginally better or un-noticeable to others. Some see a differnece in 24p playback and others who have seen it don't know what the fuss is about. Many actually don't like THX mode (some find it too dim) while others want it. 3-D is really a personal decision again. And then some people just have to have 'the best', ie, the V25 regardless of how much it costs (but still are likely influenced in their decision about how much better it looks by the fact they paid 60% more than the S2).
Is the V25 a better set? Undoubtedly it probably is, but at a cost. You have to decide for yourself whether it is worth 60% more and the only real way to determine that is for you to see both setsbeing play side-by-side, displaying the exact same source material, either from cable HDTV and/or a Blu-Ray player. I have yet to find a place that I can do this test with my own eyes. Otherwise, if you see the sets displaying different source material at different times from different source equipment you are subject to a wide range of biases, most of which you won't even be aware of.[/b]
If anyone knows of any other differences or corrections to the above, let me know and I'll edit this post and add them.