I'm from the bay area and five guys just opened i think almost a year ago now. I've had their burgers a couple of times and they're not bad. You can order them "all the way" i think with everything on them. Standard burger with cheese or you can customize it with bbq sauce, grilled onions, mushrooms jalepenos or whatever. Sometimes i think too many choices messes me up so i usually go with recommended. The burger is pretty good for a fast food chain style burger. It's bigger than the burger at in and out and messier. The fries can come seasoned or regular and generally get a lil soggy if you like that. All in all its a good fast food burger.
In and out is also really good. It's usually my go to for a good fast food burger and it's a little cheaper than five guys. A double double meal costs about 6.50ish and at fie guys a meal runs about 9 something? At least in burlingame. The patties and the actual burger is a little smaller than five guys but they're just as good. The fries are smaller and crispier also. The thing about in and out is you can order stuff animal style, which is with grilled onions and sauce etc. or stuff off their secret menu. Do a google search and you'll see whats available.
They're both good burgers, but i i was forced to make a choice between the two id go with an in and out burger. Fortunately i do not so it really depends on if i want a messy monster burger or a dependable double double.