Pin-locks are slightly bigger around, so you may have room in for fridge for more ball locks. Pin locks are slightly shorter, so you may be able to get them in a low-height fridge easier.
To me - they money saved on pin-lock isn't worth it. Accessories don't generally work with pin-lock, there is no manual pressure release valve, and if you decide to upgrade or quit the hobby, pin-locks are harder to sell. I see them languish on Craigslist and Facebook marketplace being re-listed over and over even though the price is around $30....nobody here wants them.
Like someone already mentioned, parts are expensive. If you want to modify it a lid and posts is going to have you up to what you would have payed for a ball lock in the first place - probably more.
Overall - I'd probably go with what works for your fridge size (focus on dimensions) if it matters and if pin locks fit better, save the money.