Sadly, I bet it would be the one with the guy.
I forget the actual numbers in the study but my recollection was that the number of people who read an e-mail with a picture of a smiling person on it was significantly higher. They attributed this to a couple factors...
1. When you differentiate people tend to pause. So someone going through 20 e-mails of all text will pause on the one with a picture for no other reason than it's different.
2. People tend to reflect emotion from other people and a picture can trigger that to a lesser extent. This is a well established psychological tendency that people have. Imagine yourself walking up to a group of your friends who are all laughing at something. Even without knowing what they are laughing at you'll instinctively start to smile. Same concept.
Hence the theory that people are more likely to read an e-mail with a smiling person's picture.
So when every other marketing email has a picture of a recently-laid soul patch guy, it will make sense to send plain text again?
"No matter how sophisticated your tastes or your decision buying process are, there's a marketing profile targeting you".
Don't ever under-estimate the marketing people just because you see them trying to sell beer with girls in bikinis (or server hardware with smiling guys in suits). When it's working best, you don't realize anything is going on at all.
On average, they are not.
My advice to Dell. Don't sack the marketing guys, get better operations people.
It's marketing. They don't understand that you don't give two shits how much smiling is going on in your email. The marketeers are used to doing mass marketing to people who want $300 workstations for their houses, not people interested in buying some server hardware that they'll hopefully never see after it goes into the rack.
They don't get that no matter how many smiling guys in suits they put in your email, it isn't going to change the hardware your asking about. These people seriously believe that if they show you crappy hardware with a smiling silk-tie-guy, you'll be happy to buy it because the silk-tie-guy gives you a good feeling when you see it, and you associate that good feeling with the crappy hardware.
Sorry, ranting; we just got a new batch of marketing drones at my job who want to spam the living-hell out of our customers with this sort of garbage. I've been arguing with them back and forth about it for the last few days and I'm not making any progress.