Number of degrees is pretty irrelevant, if you just want letters after your name then why not buy your qualifications off the internet?
The BEng + MSc route would be biased slightly in favour of academia, and may require a lot more self study during the MSc part. You will have achieved learning at masters level here, which may assist if you have particularly high aims within a professional institution, or within academia. Final year projects are often very academic, and are normally individual rather than team based. If a research-based MSc, you'll possibly have very few lectures.
The MEng route tends to be angled slightly more towards industry, and while you'll have a broader education, learning will only be to masters level and not as in-depth as above. Final year activity will be largely team based, and will likely have close industrial links.
Given the choice, I'd recruit the MEng graduate, since he'll typically have more of a grip on industrial issues, teamwork, and 'real life' situations. An academic or highly research based organisation might well prefer the MSc grad (particularly if the BEng and MSc are from different institutions in different cities).
What do you want to do with your life?