When to use APEX vs ADF?

Question

Experts:
What are some example projects you've faced, where you've had to pick between ADF and APEX?
I'm wondering if you can list some factors, business rules, or senarios of when to use APEX vs. when to scale up to ADF.
Some factors that come to my mind:
1. Insane business rules, with cleaner Java implementations vs PL/SQL.
2. Many data sources, not all Oracle.
3. Huge concurrent user base, where you need to really optimize caching strategies. Stuffing data in session variables isn't always practical.
4. ?Others?
I'm not especially good at PL/SQL or Java, but I do use both from time to time.
Dan

Answer 1

Thanks Chet,
we do a lot of J2EE development, but increasingly we find that is overkill for certain clients and/or situations. And the costs of J2EE for, shall we say, smaller organisations isn't always sustainable for, shall we say, 2nd-tier business systems (i.e. fewer users, not mission-critical etc).
So any technology that provides industrial strength with a browser front-end and speed of development is immediately attractive. we've built a number of small applications in APEX (for situations with 10-20 users only), but we haven't had time to benchmark scalability. I'm looking at moving APEX up the food chain as a solution for our clients, perhaps scaling to the several hundred users in an intranet context, and/or several thousands in an internet context.
I may get our benchmarking team to do some performance and load testing to see how well it does, but I'm thinking that the scaling factors will relate to the database (which scales very well) and the HTTP server (which scales very well).
Thanks for your help on this.
Andrew