The two regulators are completely different.
If you dive cold water go for the MK17. The Mares set you indicate is a workhorse and basically a warm water regulator but there is a substantial price difference between the two sets.
If you only go tropical maybe get a better second stage for the MR12 or downgrade the MK17 to something cheaper
If you dive cold water go for the MK17. The Mares set you indicate is a workhorse and basically a warm water regulator but there is a substantial price difference between the two sets.
If you only go tropical maybe get a better second stage for the MR12 or downgrade the MK17 to something cheaper