If you are thinking about getting a 3s just for watching videos you might as well just get a 2. On eBay they are going for about $200, I think the only advantage to getting a 3s would be if you intend to do some gaming as well.
But honestly since you are here and looking to do videos get yourself a 3. I was a early naysayer on the passthrough, but I'm a convert since I got the 3. Also, the FOV is much better in the 3 than the 2/3s, that alone for me makes it worth the extra cost.