I grew up in Sardinia, and now that I live in Asia
I still go back every year. I never get tired of that amazing sea. Here my thoughts:
Sardinia is great base. I am considering it too as a base to keep a boat for Med cruising.
Any part of it has a lot to offer, so I'd suggest you pick what works best in terms of airport convenience and how exposed a marina may be (some marinas just 20 miles apart will have a huge impact).
I would advise on the NW side (Ryanair to Alghero airport is 5 minutes to Fertilia
and 10 minutes to Alghero
or Porto Conte
), all 3 have marinas. If you don't know that area, it is really beautiful and sheltered.
The NE side (Maddalena arcipelago) probably gives you even more sailing areas, but Olbia airport is not as close to the marinas as Alghero airport and it gets really too busy for me. I really like the area, but to put it in perspective, I chartered a boat last summer (last week of August) and could not go to places I wanted to because it was jam packed and where I found place to anchor
, it was so busy you had to be careful not to be hit every half hour. You should go there, but to really enjoy it I would only suggest it for the low season (Until early June and from September).
Places that are more exposed to weather
and may spoilt your flight over are Capo Testa and Bosa (both very nice, but just more exposed).
Let me know if you need names of specific marinas or have other questions.