First I will point out since plumbers who are there to see,can't agree so it's dificult to help making dicissions long distance.
My advice is call you home insurance company be cause they will likly cover the whole expense. The leak could be a small problem compared to the damage done to slab.
Due to unlimited possiabilities,we need to know a lot more. Copper pipe doesn't wear out unless you have a hot water recirculating system so I believe it's as good as new except where the leak is. Copper under a slab has no joints and is high quility soft material capiable of flexing and stretching. How convinced are you that the leak is under the slab rather than where pipe passes surface of slab where it is far more likly to leak than elsewhere? Why did the pipe burst? Is your house shifting and settling?
I don't have a good feeling about the whole situation because all line replacment is only a little more than twice what one is. You best have clear understanding in writing before starting,especially wherther you will have to bring in drywaller and carpenter at your expense. Regarding the $1k bid where you have to repair structral,would you like to update/remodel the bath anyway? Pex is cheaper and I have nothing against it. That might account for spread between bids.

Thanks for the response klem. I will try to respond as best as possible. In terms of the insurance, I did call to start a claim. But I will add that my deductible is $2500, so it may exceed the cost of the total repair. Either way, maybe not worth filing given how much I would save.

In terms of the leak, it feels rather significant to me. Not a small drip, more like gushing. I am not 100% sure it is in the slab but I did pay a guy with leak detection equipment and that's where they determined it to be. The other two plumbers did more informal evaluations, both listening in the wall and while they couldn't tell me for sure where it was, neither thought it was in the wall. Both speculated in the slab as well.

In terms of the estimate, one guys quoted about 3k for replacing one line and 7k for the whole shebang. So that seems close to your estimate. The cheapest was a guy doing side jobs, and came in at $5200 for replacing all. His was also the quote for patching at 1k. Of course, we'll need to add the cost of he shower.

I do have quotes in writing and they include patching and smoothing or texturing (depending on the wall). We'd be responsible for painting. As far as copper versus PEX, I only care about function and durability. If there is no difference, then PEX is more economical. Would either impact home value?

Anyway, thanks.

Put the Pex vs copper question to your local real estate professional for the effect on home value. From FL to MN &ND,I would think overhead water lines of any material would be far larger concurn to insurance and buyers due to freezing and flooding. I am in N TX and overhead freezing isn't unheard of and good realestate agents always mention it,if for no other reason,cold water side of facuets supply hot water when first turned on 12 months of the year. With that in mind,you can see where replacing bad line vs all lines might help make desisions.
On strictly a personal level,plumbers are at the bottom by a wide margin amoung tradesmen. That is based on having used all trades hundreds of times during a 30 year career.
This conversation is akward due to A. apearattly, noone has looked at the meter to see how many gallons per hour is leaking and B. no metion was made regarding possiable slab damage until I brought it up.