In reply to Lupine Lacuna: I've been to Corsica and Sardinia but not Mallorca. The climbing on both Corsica and Sardinia was excellent. I enjoyed both places, they have a little different culture with Corsica been more french and sardinia more italian.
I liked the scenery better in Corsica, the raging torrents and broadleaf forests going over to pine woodlands at higher altitudes.The climbing probably suited me too, Granite a bit more alpine type climbing etc (take sime trad gear!), we climbed 14 days of 16 we were there. I liked Restonica and col de bavella very much. Corte was a very nice place to eat out with and a pretty town.
I liked the people and beaches better in Sardinia and the climbing was also quite unique; we climbed Sole incantatore on aguglia goloritze which is probably one of my favorite bolted routes ever! We had a lot of fun drinking wine at local wine shops all over the place, you can take a 5l can and get it filled up from a "wine petrol pump"
I'd recommend either of the two to be honest.