effectiveness of work samples

Lately I have been evaluating the success of a series of work samples as opposed to an in depth portfolio. In many cases the best employment opportunities (subjectivity, noted) arise from ASLA Job Link, Archinect or even via Facebook. Many large firms are broadcasting their job openings to a very general, public audience and, thus, are receiving numerous applications. When 100 or 200+ applications come across the desk of whomever will be in charge of short listing applicants, the level of patience this person has to read through a full portfolio naturally decreases over time.

So, using this scenario as a basis for argument, I tend to favor a comprehensive series of work samples that highlight a few projects and a broad range of skills. However, in playing devil's advocate, the portfolio offers a much more in depth look at projects in terms of process and ability to think critically. A portfolio is undoubtedly more powerful in an interview setting when you have the chance to walk someone through your step by step process.

I suppose the big questions for rating the better option are: how powerful is your portfolio when you are not there to explain it? Conversely, how well can you sum up a project in a work sample to illustrate critical thinking and design ability?

And, how do you keep your portfolio under, say, 5mb?