The kind of carry on bag features to consider: 

Decisions, Decisions

Hardside:  -Durability;able to withstand the rigors of travel, cases are not completely water resistant but much easier to keep rain, snow, puddles and mud out of your bag. -Protection;  preventing wrinkles,valuables such as cameras/suvaners, . -The sleek look, able to support other small bag ontop and your jacket. 

Softside: -Flexibility more ideal for carry on as it is able to fit in tighter spaces. -Separation has plenty of compartments and pockets for any and all trip necessities. Front Pocket/s for its quick and easy accessibility

Exposed Vs.Hidden Wheels

As you can see the four wheels take up a lot of could be packing space the four wheels is nice you can push the bag along where the two you have to tilt and pull. On the hidden you have that extra space to pack remember the wheels and the handle is part of the measurements for the carry on any space you have you want to use that whisky. 

Inside the bag 

Depends on what works best for you the blue liner the x holds stuff in but all my stuff keeps falling out every time TSA would open it. the far right one only has one side you can pack in the other i as shallow as it look is good for underwear/boxers socks and anything thin that fits in that space. The middle is the one i have but not the spacer i dont use. but once again it is all about what works for your needs... oh yea and some of the have a area where you can hang dress or dress shirts and coats on.... there are a lot to pick from I like going to TJMax for you can get really nice bags for desent price.