I think you are forgetting Reagan was our funniest president.
Stylistic differences. Reagan was more of a strategist. Trump is probably a better tactician.
What that means is that Ronald Reagan was a better planner, and had his lines prepared for when he needed to use them. While Trump can think "one his feet" better than Reagan, and could make up humorous comments up immediately, and has demonstrated that ability.
i especially liked his one word description of his enemies, such as "Low Energy Jeb", "Lying Ted Cruz", "Crooked Hillary", etc.
For all of his abilities, Reagan would have never thought that kind of thing up on the fly. He'd have thought about it for a while and used it at the right time.
i do agree that Reagan was a funny guy when he wanted to be.
The one time that Reagan did think fast was during one of the debates against Carter, when he made the comment "I paid for this microphone!". That probably won the election for him.
However all things considered, i think that Trump is better at improvisation.