Ideally a squared stance has these positions and negatives:
Pros:
- better for checking leg kicks
- better for throwing leg kicks
- better for throwing elbows
- more powerful jab and hook
- faster punches and combinations
Cons:
- leave more surface area to the body
- punches may be faster but the hyper-extention of your arms will be shorter, thus your punches will not have the same reach they would have had in a bladed stance
- limits head movement
As you can see, if you are a boxer and only a boxer then the traditional bladed stance is most definitely the better option, as you do not need to worry about kicks or elbows, and it better defends the body and allows for greater head movement.
If it's MMA or kickboxing/Muay-Thai, you can play around with it a bit. No fighter uses exactly one stance. Sometimes, a cross between multiple stances is the best route, especially in MMA.
I personally like the squared stance, but I will also transition into a slightly bladed stance at times too.