It has arguments both ways.
Yes, it would be nice to always save/heal with 25 con or whatever they had it at with out regard for having died x amount of times.
But it also makes sense that dying takes its toll on you physically and that after dying 40 times you would not be as naturally hearty as someone who never had.

Another perk of high con is the potentially high number of deaths you can take without ever having to train con. If you start with 23 that is 60 deaths you can take w/o trains, which is a lot I would say. Con gear is extremely easy, so walking around with 25 con is easy if you want to gear that way. Having that kind of longevity is a little bonus, and maybe allows you a little more risk taking since deaths are far less of a problem for a dwarf than say an elf.

I would say dwarves having the ability to always have 25 con is the advantage, but to use it they have to gear for it. Just like an arial gears for dex and fire giants for strength. Dwarves have other nice features too I'd say.