I'm kinda partial to hard cases. My daily case is a beat up It's George 2x4. I estimate it to be at least 20 years old. I find the protection to weight ratio hard to beat. The side pocket doesn't hold much, but the lid/cup is a handy place to store my car keys and phone.
Here are some example of of the hard case styles.
Starting from right to left.
2x4 Centennial, no strap for hands free carry
Adam 2x4,
1x2 J&J soft case, the shoulder strap is very handy
1x2 Fellini, I find leather gets scratch up too easily. So, not too pratical
1x2 John Barton 'cigarette case. I believe these were prototypes, as I haven't come across another. Looking back, I should've grab the 2x4 when I had the chance.
2x4 It's George (back-up in case the black 2x4 wears out).
a couple of 1x2 and 2x4 Ron Thomas. I like how his straps go down the broad side of the case.
1x2 McDermott. Made of aluminum, built like a tank but no strap for hands free carry.
a couple of Brunswick 'fishing rod' cases. Compared to other cases, not very practical
1x2 It's George that I outgrew. Maybe I started playing 14.1, it would be a practical daily carry.
Drawbacks, anything bigger than 2x4 and the hard cases gets unwieldly and looks ugly. If I need to carry more than 3 cues, I break out my 3x6 Jim Murnak butterfly, or 3x7 Jack Justis.
Protection is not that big a deal to me as all cases I have used/seen protect cues adequately for my uses.
Function to me is a matter of choosing the features I want. How many cues, how many pockets, pocket size, soft case, hard case, etc..
Weight is only an issue for me with cases designed for 4+ cues. I like soft side cases for this.
Style is where I make much of my decisions and everyone has their own taste. Custom is nice, but I am not a designer. I know what I like when I see it, but I'm not an artist. Another consideration with custom is how long it takes to make and if promise dates are met.
I own an 3x6 Instroke, 4x8 JB Butterfly, and several inexpensive 1x1, 1x2. Style wise I like Volturi, Justis, Melton, Eastwood, but I don't own any of them.