I went to Palmilla last August and really enjoyed it. Before that I spent a significant amount of time in Punta Mita, including at the Four Seasons.

I would recommend Palmilla over FS. The rooms at Palmilla are more recently renovated, the on-site food selection is better and I found the staff much friendlier. On the other hand, Punta Mita has a better beach (especially if you want to swim in the ocean) and tennis. I also prefer Palmilla because of the greater variety of restaurants and activities in Cabo San Lucas and San Jose. There are some great restaurants outside the gates of Punta Mita but selection is limited.

You can easily arrange transportation/cab in both places. Summer is going to be hot and humid in both places, but Punta Mita is more tropical and will be the hotter and wetter of the two.

I would think 4/5 days is probably the max at Palmilla if you don't plan to leave the property and are not big golfers.