AGK from what I understand was built with DB at its core in terms of syntax and coding methods... So the choice is yours... Note DBP is 3D and AppGameKit will be 3D soon however the functionality will vary... Also note DBE will basically build upon DBP... So the logical path would be DBP > DBE and pick up AppGameKit in between... I bought AppGameKit a year ago still not touched it as it still lacks the functionality I require although network commands have been built upon... I just need a method to playback Video... In Tier1...
Hope that helped...