Archetypes vs. Dexterity for new content types and new field types
As the initial developer of Dexterity, I'm quite biased, but:

Dexterity is cleaner and more 'modern'
Dexterity is more consistent with the rest of modern Zope and Plone
Dexterity has less boilerplate and Dexterity types generally use less code
Dexterity lets you evolve from through-the-web schemata to filesystem development without throwing away your work and starting from scratch
Dexterity arguably has more/better documentation than Archetypes (see plone.org/products/dexterity as well as my book Professional Plone 4 Development)
Dexterity is stable and seems to be the preferred choice for many 'new' projects

These points are basically the reason Dexterity was started, so they're not accidental.
Archetypes will certainly not go away any time soon, and will probably exist as part of Plone core and (possibly, eventually) and add-on for a long, long time. At the end of the day, you can see them both as different ways to create CMF types, which is all it is underneath.
I think the main decision point right now, apart from any legacy concerns, is multilingual support. There is no good story to replace LinguaPlone, although there are some efforts underway to try to rectify that.
Martin
I've been out of the Plone world for a few years (since about Plone 2.5) and I'm trying to get my bearings as to where to invest my time creating new content types, specifically, with new custom fields (including custom view & edit widgets).
Can someone help me understand the decision points between Archetypes versus Dexterity?  I've written AT-based products before, so I've got some familiarity with the infrastructure there.  I'm also slowly dusting off my Zope 3 memories.  Some specifics:

What does the future look like for Dexterity versus AT?  Is AT going to be replaced by Dexterity?  If I write an AT-based product, will it need to be ported to Dexterity eventually?
What provides an easier developer experience for custom field types, custom widgets, and custom views?
How does deploying a custom workflow with Dexterity work?
What about migrating existing content from an older version of my product to a newer one?

Thanks!