I dont mean the combat so much, they are comparable in that GURPS is far simpler if you want it to be but if you want detailed combat with tactical choices GURPS gets more involved. Though I like the choices and fights can be done without checking a single book if you know your weapons and choices.
The character building is what I was surprised by. Old D&D you pretty much added a proficiency and HP as you leveled up, maybe some new spells depending on class. Pathfinder adds variety (which I like) but uses a Feat and skill system where you get new choices at certain levels. Trouble is your limited in choices and amounts and some require others as prerequisites. Choose the wrong thing and you may never be able to get a specific desired one.
In GURPS which is point based instead of class and level based you have two character design techniques.
1) Normal is pick from whatever is allowed in the campaign that you have the points for, This lets you customize in a wonderful way but can be overwhelming and lead to decision paralysis. You have so many options, it can be tough to decide what to choose.
2) Professions use templates with shortened lists, so similar to a class system but more choices are available. This makes building pretty quick as each profession is designed for a certain party role and the most important abilities are required in the template or at least strongly suggested. Good templates offer lenses or a paragraph describing subtypes to help the player choose.
As you gain experience you add items from the template and ignore other options. That helps protect party niches and roles.
GURPS is frnt loaded, meaning you do most of the work in the beginning, Pathfinder is back end loaded meaning you start really simple and add later. This makes GURPS more complicated when starting (Though that is reduced if you use templates) but your more adaptable as the game goes on and you can choose more freely. Pathfinder you pretty much need to plan ahead and have far less choices that will make your character unique and special.