WHen I drive from Orlando to Miami and back, I always use 1-95. Some people say that the FLa-Turnpike is nicer and not so crowded. Maybe so; but I never thought that 1-95 was that bad (Until I got near Miami around rush hour). However, over-all, the trip on I-95 went smoothly both ways for me.
One thing that is better about I-95, over the Turnpike, is the cost. When I use I-95 it is free (except of course, when I use the Beachline Expressway to get from Orlando to I-95 which costs $2 in tolls one-way).
The Turnpike costed me $13 in tolls one-way (and that was 8 years ago, when I last used it).