Our lab has been using Collagenase I (from Worthington) for at least 15 years to isolate HUVECS with no worries. we do batch test every 4-5 years work out what works best or at least doesn't change the isolations and then order in a number of bottles. I'm not sure why collagenase I over the others but there's some info from their website about the different types (it could be as simple as cost):

Type 1 crude collagenase has the original balance of collagenase, caseinase, clostripain and tryptic activities.

Type 2 contains higher relative levels of protease activity, particularly clostripain.

Type 3 contains lowest levels of secondary proteases.

Type 4 is designed to be especially low in tryptic activity to limit damage to membrane proteins and receptors.

Dear Michaelia Cockshell,

Thank you for your informative answer!

I learned a lot about various collagenase thanks to you!