This is a hard one,as both of them are great people outside of the ring,but of them are good on the mic,and both of them has some classic match!I prefer Shawn Michaels more,and their is some reasons why:
Shawn is better on the mic,and better at cutting promos.Bret was also good on the mic,but It just seem like he repet the same stuff everytime!Also is promos was good,but no more then that,I enjoy his promos with The Hart Foundation,but his promos alone was almost the same everytime!
Now on the other hand Shawn promos were always great to watch,he always make you laugh or make you cry,he was great on the mic overall,and he knew who to work a crowed better then Bret Hart,although Bret was good,but HBK is great!personally I enjoy watching HBK promos and I enjoy watching him talk on the mic,because Bret just bored me when he is on the mic!
Now on the wrestling part,their is no doubt that Bret is a better teachnical wrestler,and one of the best,alot of his matchs are great,and he could carry big guys with poor wrestling skills t a good match!Bret could always find a hold or a submission to cause more damage to his oppennent,and I like the way on his matchs were he was jusst working on one body part for most of the match,and it was usally the leg to set his rivals to the Sharpshooter.But same has his promos I felt like he is repeting the same stuff again,and again,and he didn't made some kind of a surprise new move sometime!I enjoyed alot of Bret Hart matchs,but there was a couple that just looked alot like others!
About Shawn Michlaes,I think that he is a great all around wretler,and their is that feel of excitment every time he wrestles for me.I know that he repet a lot of moves in the ring,but he does add some new moves to his move-set from time to time,and I found alot of his match better then Bret matchs!I enjoy watching Shawn wrestles more because he always brings his chrisma to the ring with him,and almost everytime he is in the ring,either as a face or a heel he knew who to draw heat or draw pops from the crowed,and he know who to get the crowed into his match!
So in my opinion I prefer Shawn Michales over Bret Hart,although Bret is also an amazing wrestler,and a great person overall,but Shawn is just better in my opinion.