You know, that's a great question — and we don't have a great answer for you. Historically speaking, PC laptops were much more accessible for upgrades than Macs. But it is 2013 after all, and things may have changed significantly, given how fast technology is pushed out to people.
(Note that upgradability does not equal repairability, as some easily-upgradable laptops are absolute bears to repair/maintain, promoting some users to even write a song about it.)
Here's part of the problem (that we also encounter with Android devices): We can spend $10,000 for various PC laptops from various manufacturers, and not even scratch the surface because there are so many different models. For example, is the Dell Inspiron 15 the same as the 15R in terms of repairability? What about the 14R and the 17R? It gets complicated — and expensive — really fast.
So, aside from the completely non-useful "sorry we can't help you" statement, I'll say this: you can at least look at a manufacturer's website and see if they have a service manual for their machine. This will help you tremendously if one day the machine decides to take a swim in the pool. Dell and HP have been known to publish these manuals, but they may not be the only ones. Running with the example above, here's the Dell Inspiron 15 owner's manual that includes full disassembly information.
That way, you can at least look at the service information and determine how fixable a particular laptop will be. It's not as hand-dandy as a score/summary assigned by us, but it's a step in the right direction.