The second one offers more upgrade options since you have a h97 motherbard sou you can add something like the 4690k in. i have a simmilar cpu to the one in the first build (i5 760) and it is a bottleneck in more demanding games with the gtx 970.
If your aiming at a budget gaming PC, then that is as budget as you can go and not too bad build to boot, although I would also recommend you put in some extra RAM. Games are starting to lean over to a minimum of 8Gs of RAM. GTA V for instance wants 8 GB.
Yes it is upgradable. The PC in the video link you gave us is using an older processor, but the overall PC should be faster than the one in the second link, if you add a bit more RAM
The second one offers more upgrade options since you have a h97 motherbard sou you can add something like the 4690k in. i have a simmilar cpu to the one in the first build (i5 760) and it is a bottleneck in more demanding games with the gtx 970.