What's the main difference between these two designs?  I know that the low profile is far more common but there are still some of the old style round reels being sold as well but not nearly in the same numbers.  So what's the big advantage to low profile reels that they are the most common baitcasting reel design?  

ergonomics, fishability, and probably weight.

ergonomics, fishability, and probably weight.

everything he said. some of those reels needed a light rod to cast your bait well. i still use a few of them for big, heavy baits

ergonomics, fishability, and probably weight.

x2,and they are easier to hold/palm and more comfortable on long days of fishing.roundies are tanks and built to take beatings and ment to winch in the big girls from the nastiest slops and downs imaginable

I fish with, for the most part, 4 4600 C3's and 2 REVO SX's.  I went from 5500 C3's, to the 4600 because of the weight about 4 years ago.  I like both styles, but the SX's are lighter.  They cast the about the same distance.  The drag is better on the SX and the SX does feel better in the hand.  The SX's handle lighter lures better that the 4600's.   The SX's are about double the price of the 4600's.

Just trendy. Most of my baitcaters are low profile, but two of my favorite

are CTE200GT. They perform the same and feel the same in my normal

(medium) hands. You will have to play with them yourself to see which

you like...I like both!

8-)

I like both. I can palm a round reel a lot better than I can a low pro, but the low pro weighs less, and can be used for many different patterns . The high end calcutta's are awesome, and the old millionaire reels with mag brakes are great reels also.  

I like em both but these days my preferences have been on the round side. I have large hands so i really don't have a problem palming a round reel. It's mainly a matter of style preference and some weight consideration. The Calcutta series from Shimano are built to last, if you look into a round reel keep em in mind.

Line capacities and generally strength. The round reels of a good quality will be stronger than a comparable low profile. Weight is also a big difference. I look at round reels as my setups for heavier lures and bait fishing.

For many years all i used were round Abus and loved them. Than i got my first low profile and the rest is history!!!!!