I am in the same fix you are. Wondering what to do.
Well, I have heard both. The Sony 260 definitely sounds a little better too my ears. Cleaner/Crisper/more loudness. The VIZIO sounded a little "muddier", and not as loud. But it still has that 5.1 surround from at least 2 sources(Cable box/Blu-ray or gaming setup) DIRECTLY CONNECTED TO IT.
BUT YOU MUST GO DIRECTLY FROM YOUR SOURCE TO THE SOUNDBAR TO GET 5.1 SOUND. So you would have to go from your Cable Box/XBOX360/Blu-ray/etc... from either the OPTICAL/COAXIAL OUT DRIECTLY into the Soundbar fro 5.1.
Samsung, along with nearly all(not all, but most), DOWNGRADE 5.1 input from HDMI in, to 2.0 stereo out from the OPTICAL out from the TV. ONLY when you are using the TV's internal OTA tuner(I do not know if it works with unscrambled QAM signals from the cable co, but it might), will the OPTICAL OUT from the TV send 5.1 surround sound.
This is where VIZIO messed up a little IMHO. If the new version comes out with MULTIPLE inputs like 2-3 optical in, AND 2-3 coaxial inputs for multiple sources.
You may be able to buy a OPTICAL changer, or something that passes through multiple optical/coaxial inputs to the VIZIO to help this dilemma, but I do not know what they cost, or if they passthrough 5.1 sound. Seems like an unnecessary added expense. These things are supposed to make life easier, not harder.
Here are reviews by CNET about these systems:
Sony has the HT-CT660 which has HDMI and multiple optical/coaxial inputs, but it goes for $100-$125 more than the 260.
I may just wait for new version of the VIZIO to pop up in 8-10 months which should have more inputs, and/or HDMI inputs added to it.