I think Kasparov would have`won easily  

It's just impossible to tell. They would have had to play each other not just once but many times for us to judge who was better. Even then, it may be hard to tell because some players just don't get along against certain others, even though they are absolutely brilliant in general. For example, Tal was an amazing player but struggled against Korchnoi. They would have had to play in the same era for an extented period of time with chess theory at the same level of advancement and the same access to resources against the same opponents for us to know for sure.

they have different styles but i tend to think kasparov would come out better. his ability to spot combinations is terrifying.