Main difference btw regular vertex best and vertex st is the strap on st will break off at lower force because it's meant for ground use.
The newer vertex best has a slot for headlamp in the front and new two wheel adjustable suspension. Old vertex best has rear one knob adjustment. My old one has grey patches, the new vertexes look like they have black.
None of the vertex best series is UIAA approved, if you care about that.. The vertex/alveo vents are approved.
Best models are for use around high voltage. Best has an E classification. That is the only difference. C= Conductive G= General .....good for up to 2200 volts E= Electrical .... good for up to 20,000 volts
If you are just climbing, and not working, who cares!
My alveo measures 73cm whole circumference ,it's a little big and sits too high on my head since I have to go through tight spaces at times it gets in the way.
Are all the vertex best models the same size? ( circumference of the outside helmet) as the alveo?
Are there any manufacturers of smaller helmets ? (cannot have vents)
My vertex is the same size as your alveo. I can't find anyone else making class E helmets for climbing, the KASK ones are vented... You should probably ask your management what helmets are allowed PPE for your job...