XL4 comes in two flavours, save the Ocea design one with only engraving being the difference, the XL4, AKA DB4, standard has one hp port whilst the XL4 plus has two hp ports.
Internally is identical to a DS4 but environmental sealing end has changed, they are using a newly designed end cap and there is no longer a separate environmental diaphragm.
On the DS4 a c pin spanner was required to undo the enviro sealing cap but now a special tool is required.
There are now O rings protecting threads from contact with water on both ends of diaphragm clamp. It's a nice touch.
Still no removable crown.
Same service kit for DS4 and XL4 (DB4).
It's a slightly "better" design than the DS4 but not by much. Only real plus for me is the introduction of the second hp port on the plus version, but boy you're paying for it.
Personally if buying as first stage only, assuming DS4 is still cheaper, and if you didn't need the second hp port I'd be buying a DS4.
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