Doing some searching on Google I found the following prices for 2014. The prices for just the concerts are pretty comparable between the 2 parks. It's the Rock Your Weekend tickets at Universal that are the bargain. With
free dining though I can see not wanting to leave the "bubble".
Night of Joy
Single-night tickets are $59 plus tax in advance and $69 plus tax on the days of the show. There is also a two-night ticket option, which is $108 for both nights and includes a 1-day admission to one of Disney’s two water parks or DisneyQuest Indoor Interactive Theme Park if you purchase them through August 5.
Rock the Universe
Rock Your Weekend ticket – $120.99 plus tax
Both nights of Rock the Universe at Universal Studios Florida
Three FULL days of single-park admission (one park per day)
Rock Your Weekend ticket with Park-to-Park Access – $160.99 plus tax
Both nights of Rock the Universe
Three FULL days of park-to-park admission
Park-to-park access all weekend
Rock Your Weekend tickets are one of the best values Universal offers to the general public all year long considering that a regular 3-day ticket is $145.99 for single-park access or $185.99 for park-to-park access. The Rock Your Weekend tickets are roughly $25 less expensive, and they include the Rock the Universe two-night event!
2-night event – $95.99 plus tax
Both nights of Rock The Universe at Universal Studios
1-night event – $57.99 plus tax
One night of Rock The Universe at Universal Studios