Em's are more pure pinball than DMD's. DMD games are great and some of them are certainly more fun than EM's, but an EM is fun like Checkers is fun. An EM pin is the essence of what pinball is all about, the randomness of the ball, trying to get a higher score than somebody else, or the last time you played the game.... the artwork on just about any EM, the total package of the cabinet design, backglass, lighting, and artwork is usually more attractive than all but a few DMD machines.
With all due respect to the modern designers, too, I'd say that the design of most EM's is much more creative than most DMD games. Not necessarily from a gameplay standpoint but from an engineering stand point, some of the things in the games are genius.
Williams' Hotline... had a grid in the middle of the playfield with lit rollover targets. Using just relays and motors, the game lit up the letter "H" on the grid... when you rolled over all those targets, it reset and lit up the targets to spell "O"... then "T, L, I, N, E" as it went on. How in the world did they ever think the engineers would be able to pull that off with switches and relays??? ... but yet it works. Brilliant design.
There's a simple mechanism in some Williams games that has a little wheel at the top left of the playfield. Depending on what color is lit on the wheel, it changes the scores of every target on the playfield! So if it's yellow, all the targets are 1 value, if you make the wheel move to red, now each target is worth twice what it was before... or ten times what it was before, and they're all different values. How in the world did they make that work with just relays?
Look at some of the designs Bally did in the mid 60's, all asymmetric with gates and pop bumpers, mushroom bumpers all over the place. On Bally's Dixieland, the left drain starts at the top of the playfield! There's two gates that open and close on the left, and if the gates are closed your ball is saved back to the playfield.. but if both gates are open, and you lose the ball to the left at the top, it falls 3 feet and drains!
Look at Gottlieb's "Gobble Holes" on some of their games... heck, look at their whole Add-A-Ball concept. Brilliant!
There's a Bally game called Capersville that can start multiball modes, on an EM, by having captive balls in saucers at the top of the playfield. Several other multiball games, too, it's just amazing what they were able to pull off with only relays.