I think Kuki's points are excellent and right on the money.
My only quibble is that I wouldn't even try to do as many places on a 10-14 day land tour as a Mediterranean cruise of equivalent length does. I'd pick maybe three places and do four or five days in each. Because Kuki's right that if you tried to do as much "geography" on a land tour as a ship typically does, you'd be a babbling idiot by the time you got home.
I think instead that the comparison is whether you want a more in depth look at some of the important places, or a once-over-lightly look at a lot of places. I'm not saying that one is right and one is wrong, just that I think that's the real choice.
Other things to consider, of course, are how brave a traveler you are. If you're truly concerned, for example, about how you'd cope in a country where the language is other than English, maybe the cruise is for you. If, on the other hand, you're generally comfortable with various kinds of travel and know how to roll with the punches, you'll be greatly rewarded by more leisurely looks at some of the European/Mediterranean centers of interest.
Some of my most memorable times in Europe over 35 years of going there are the times I've spent on leisurely walks, at fine restaurants and sidewalk cafes, at great museums and off-the-beaten-path hideaways, and having the time to meet people. As Mark Twain said, people who travel to each others' lands never hate each other.
There was an interesting article in the Wall Street Journal last week pointing out that the more upscale cruise lines are doing more and more itineraries with extended port calls at significant places, often multi-day. Naturally, they see more revenue in more elaborate shore excursions, but I think they may also be realizing that discerning customers don't just want to be driven through a world capital then be herded back on the ship.