When rolling out a SharePoint training program, is it best to go with external or internal training?

I would agree with John and add a couple of other thoughts. One of the trends I am advocating a lot out there is the concept of 'just-in-time' training. Otherwise reference-based training that broken down into small snippets that provide you the information you need for the task you are trying to do.

Where in-class training is great, the problem is the amount of retention that a user actually retains. One of the expectations of classroom training is the user goes straight back and begin apply what was learned, which is often not the case. Adding a 'just-in-time' training layer can increase the overall success of training by giving users access to materials when needed, instead of part of a curriculum. For example, a user needs to create a list for their SharePoint site and have access to learning materials around creating a list.

This type of training can be accomplished by creating your own videos / resources or by looking at one of the commercially available products, such as the End User Adoption Solution by Combined Knowledge.

Have a comprehensive training strategy will go a long ways to make your deployment an overall success!

Speaking for end user training only in my answer :

Internal is better if you have the Right SharePoint trainer in-house, a dedicated training centre, system in place to manage the training, and decided who will pay for it all. The benefit is that it can work out cheaper, you train on your own platform, you can tailor your training to your governance rules and give one message. The downside is that users don't always take it seriously because they can run out to do work and cancel at the last second because they don't see the billing. There are often network / facilities issues inhouse to be overcome too.

External training does allow for more concentration - but if you use more than one external training house, your users will be given different messages by each one and tend to get confused about what to do when back at the office because of that. Business have their own budgets so can go to anyone they like. External training is done on default settings and branding, if the company has a different look and feel, users won't know where to find settings they were taught at the training house. However they have the infrastructure in place to facilitate classroom training, which most companies don't have.

Pros and cons on boths sides.

I agree with Virgil - if at all possible, just-in-time training is the best way to ensure that users will retain what they learn. That's a bit easier to do for end users, but developers will definitely need more focused training. Most organizations I know do a combination of in-house and external training, often with a combination of focused classroom training with just-in-time learning modules a follow up. One of my clients did a weekly "Get Sharp on SharePoint" focused web-based training session for 30 minutes each week the first year after they launched. Each session focused on a single topic that was publicized in a schedule so people could choose which session to attend. They recorded all the sessions so that if you missed one, you could watch it later. It was really effective - and allowed the trainers to collect a lot of good feedback about how SharePoint was being used and where users were having challenges.

There is some information - like educating users about the governance plan - that will be hard for external folks to deliver. At the end of the day, I think the best way to go is a combination of internal, external, classroom, online, and just-in-time training, which is basically the classic consultant answer to any question - "it depends."