I think standard Freeview through the antenna now has 50 channels (compared to the total of 5 terrestrial channels we had a few years ago before Freeview existed and the 4 channels we had up until 1997!), so I guess it depends on whether or not you're happy with just the channels offered on Freeview or if you want the extras offered by Sky .
Personally, I decided to go with Sky over Freeview because there were some channels I wanted to watch that weren't available on Freeview, plus I've also got unlimited broadband, a Sky+HD box and a phone line with my Sky package... so for me it was better value to get the Sky bundle all together rather than having Freeview and paying for internet and/or phone separately.