There are some give and takes with the changes in Infinite. I actually liked BioShock's "FUCK IT, YOU CARRY ALL THE WEAPONS AT ONCE" design choice, as it allowed me to experiment more with weapons I normally would have used maybe once or twice. I understand why Infinite only let you carry two weapons at once, but that led to me using only a small handful of early game weapons I had already upgraded.
I thought vigors were a fairly major improvement over plasmids. Each vigor had advantages and disadvantages depending on the situation. In Bioshock, there were simply too many plasmids that basically did the same thing. For example, there were three "aggro" plasmids -- one for splicers, one for turrets/cameras, and one for Big Daddies. Vigors cut out the redundancy.
I could go further, but I'm too damn tired today to write a thesis comparing BioShock's combat to Infinite. I think Infinite fine-tuned some problems found in BioShock regarding enemy health and plasmid redundancy but could have done more.