Well, playing it on a DVD would mean exporting all of your videos to SD and compressing them down to MPEG2, then burning them all off. It's a time consuming process that will leave you with SD content - not your nice HD.
Or, if by disc you mean Blu-Ray, then the bluray will look better, but will take longer to compress etc _ blu Ray discs are expensive.
Or, if by disc you mean putting the camera files directly on a DVD, then that will look great, but I believe you only get 30mins per disc, + you need a Blu Ray player.
There are other players out there besides the Apple TV, for instance Popcorn Hours, Boxee boxes etc. Some TVs even play the camera files straight from a a pendrive / USB harddrive via a USB port on the back of them. But, if you already have a Mac and you are already using iTunes + iMovie, then the ATV is a really easy way of viewing content with very little hassle involved in compressing and exporting and a very shallow learning curve, as they are all designed to work properly together.