6 pt sockets and wrenches are stronger and less prone to breaking, cracking or worse still, stripping the head on a bolt. Used where more torque is needed such as very tight or frozen bolts, high torque bolts such as head bolts etc. The disadvantage is that they can only slip on the bolt at increments of 1/6 of a turn, this can be a disadvantage in tight places.

12 pts are more versatile in that they slip on in increments of 1/12 of a turn. Easier to use but will strip the bolt easier than a 6 pt of equal quality when you really have to put the muscle on it.

If starting out it is important to acquire high quality tools that just do not ever or rarely break. Cheap tools will cause discouragement and frustration. Start with 12 pt sockets and wrenches and get 6 pts if and when you think you need them. I do 90% of my work with 12 pt because most of my collection is 12 pt, only own a few 6 pts.

I feel sorry for those guys who proudly display huge kits containing hundreds of pieces of cheap no name tools made in China. If on a budget buy just a few of the most common sizes a few at a time as you need them in 3/8" drive, 1/2" drive for the larger sizes. High quality only. Sears Craftsman brand is quite adequate for average use, better would be Snap On. Of course every mechanic have their favorites but this is classic case of you get what you pay for.
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David Hunter