1. (CH3)3C+ is more stable than (CH3)2(CF3)C+. CF3 groups are EWG (electron withdrawing groups). The CH3 groups are EDG (electron donating groups) which help stabilize the carbocation. Electrons are negative which make the carbocation less positive, thus stabilizing it. If you have EWG's instead, you lose that donation of electrons to stabilize the carbocation.