mm... very hard to decide
In this case, it really depends on you, if it was me, I'll get the V570, it'll be fun to use the MPEG4 video and panorama shots in disneyland, much more fun than using image stabilizer.
Image quality wise, even though the T9 probably better, I think it's not worth to sacrifice the 23mm, since both are ultracompacts anyway.
Well... here's the deal, you can do anything the T9 will do with the V570, but there are too many features of V570 you cannot do with the T9.
Image stabilizer is nice to have, and it's fun to play with as well, but again.. its a matter of personal preference.
For shooting disneyland lights, I'm confident that V570 with ISO400 (use noise reduction program later), at 1/20s will do a fine job.
If I could suggest you another way, since you have loose budget, get the V570, if you later found out you REALLY need the IS, get another panasonic sub $200 stabilized camera, this will give you both features
I have many cameras, but I'm still thinking to get V570. I have Sony W1, Panasonic FZ5, Sony H1, and still wanting a V570