Pros and cons are pretty obvious, but I'd like to point out that both the York spinlocks and Cap spinlocks you linked to are essentially the same type of dumbbell. You've got two classes of dumbbells:
The pros and cons of non-adjustable dumbbells like the hex dumbbells you linked to are going to be the same whether the weight is rubberized, circular, hex, etc. However, with adjustable dumbbells you have three basic types: spinlocks, tool adjustable, and "dial-a-weight". The pros and cons are more varied between these.
First the pros and cons of adjustable vs. non-adjustable weights:
- adjustable weights are more easily stored
- non-adjustable weights are easier to use when you change weights within your workout
- non-adjustable weights are more robust/solidly built
- non-adjustable weights are cheaper per pound when comparing one dumbbell to one dumbbell, but you have to buy more of them, so a whole set will be more expensive
- Hex vs. round weighted ends: the only difference is that hex won't roll on you, but for the majority of dumbbell exercises that really isn't much of a concern.
So, if economy is what you need--either space or overall cost--adjustable dumbbells may be the way to go. They are more cumbersome to use when you have to change weights during your routine, but that can be offset by getting enough handles/weights to support that. However, non-adjustable dumbbells are the most solidly built and the easiest to use. There's no moving parts. They just take up a lot of space, and a whole set will be very expensive.
Between the adjustable dumbbells, the pros and cons are more varied:
- "dial-a-weight" dumbbells (including bowflex, the "powerblock" and other similar products) are the most expensive per pound
- "dial-a-weight" dumbbells are the most complexly built dumbbells--which means they will break easier, and in ways you can't really fix.
- "dial-a-weight" dumbbells are easier to use when switching weights in the middle of your routine--but that can be offset by having more than one set of handles with the other adjustables.
- spinlock dumbbells are the happy medium between dial-a-weight and tool adjusted. The spinlock is easy to remove and put back on, and doesn't equire any tools, but you have to spin the lock all the way off the handle which is long. They are more solidly built than dial-a-weight, but not as strong as tool adjusted dumbbells.
- tool adjusted dumbbells can be every bit as strong as and well built as non-adjustable dumbbells.
- tool adjusted dumbbells are the least convenient to change in the middle of a workout because it requires using a tool--which can be easily lost.
- you are not likely to find new tool adjusted dumbbells due to the success of the spinlocks.