Brakes: hydro or mechanical for new build

[Bobonli]

I will very likely build a new mountain bike this year with a primary intention of bike packing and non-technical riding. Is there a consensus about brake system: hydraulic versus mechanical for this application?

For added context, I'm not going to be an international traveler. We're talking local overnighters, maybe pack the bike to visit relatives in AZ type of thing, so I think from a parts replacement point of view I will never be too far from a legit bike shop.
I'm currently running Shimano hydro on my 650b road bike, and 11 year old XTR mechanical on my current mountain bike. The hydro is a bit better and so far has been free of any issues, but I certainly don't abuse that bike in mud or dust or running over rocks etc.

Is there any reason not to choose hydro, taking expense out of the equation for the time being?

[KittyOnMyFoot]

Other than being nigh impossible to fix in the field (depending on the failure and your willingness to carry a spare, pre-bled cable/caliper set), I can't think of one.

[Adam Alphabet]

I can only think of a very small set of circumstances where I would go back to mechanical disc brakes. For the intended purposes/usage you've outlined hydros 100%.

[Salubrious]

You probably won't run into hydro problems on a day trip unless you don't keep them serviced.

There are three issues you can run into: seizure of the caliper, seizure of the master cylinder, and boiling the fluid. I just read of a guy on the TDR (2016 Corderilla) that had his caliper seized. My GF broke a rib in the Tetons a year and half ago due to a seized master cylinder. I boiled the fluid on a long rough descent on Colorado... In these three cases luck played a huge role in things not being a whole lot worse!

My current build has cable operated brakes and I will never do hydro again.  Each his own...

[Bobonli]

It's my understanding---and correct me if I'm mistaken, that those malfunctions are relatively rare.

There was a lot of concern about boiling when hydro discs first came to road bikes. I for one held off switching out of concern but over time I couldn't find a single person who had that happen to them. I'm not saying that it doesn't happen, it obviously happened to you, but I think the numbers are pretty low.Similar to people overheating their rims with rim brakes.

[Salubrious]

^^ Yes, they are rare. I'm not in the bicycle service industry, but in servicing some friend's MTBs I've encountered frozen calipers and master cylinders several times. In one case the brakes were covered by warranty- the bike was only a year old. Other than that case, the usual problem is dust getting past the seals, and if you are on something like the Tour Divide, its going to happen; whether its enough to cause a failure is a different matter.

But many of these ultra endurance courses put you out in the middle of nowhere (if not often you can see it from where you are); if you really did have a problem you might rethink whether going hydro was worth it. On my last build I used 203mm rotors as generally the brake pads run cooler and so last longer; if you are planning a hydro system I would go with the larger rotors. But I'm conservative about these sort of things.