Help Choosing Between Scubapro MK19 and MZK25

Hey folks!

I'm looking to replace my aging regulator with a new setup. I'm interested in diving the meg ledge a couple times of year where sediment will likely get stirred up quite a bit. My local shop is recommending the MK25 and not concerned about the lack of environmental seals. Will the MK25 in fact excel in this environment or should I sway towards the MK19?

Additionally, what regulator(s) should I consider for a backup?

Thanks!