Sewing Machines: Mechanical, Electronic or Computerized?

I have been shopping for a new sewing machine to use for my classes. I have been using ancient Singer and Kenmore machines, which work fine, but I have decided to modernize and teach my young students on something they may be more likely to feel confident using. The one feature I really find does this is the speed control. Several years ago I invested in my first computerized sewing machine and it had this feature. So which is the best machine to get? I want a machine that is simple (not too many stitches and NO embroidery features), has a speed control, is lightweight, and cost around $250.
The adventure begins:
Computerized vs. Electronic/Mechanical
Well, who knew this would be so complicated! All of my machines are electric, and I thought all new machines were computerized. Not so. A computerized machine may be a low-end model or the most expensive embroidery machine. An electronic machine may be high end as well. As an experienced sewer, but inexperienced buyer, I found this all very complicated to navigate.
Facts:
The difference between Mechanical Machines and Electronic Machines is basically semantics. CLARIFICATION (added 1/11/11): mechanical machines have no electronic guts - they have gears and levers and pullies and such. I was thinking electronic meant you plugged it into an electrical outlet. Silly me! Electronic machines are different from a basic mechanical. I'll work up a post about this with better information... Most dealers use the term electronic, but once in a while you will hear some one say mechanical. These terms are used intermittently in descriptions as well. This was terribly confusing to me at first. I asked many experienced sewers I knew what the difference was and it became a giant guessing game. Here is what I've decided: A mechanical machine refers to older or vintage machines. The user has to adjust the settings, the tension and stitch length. It is more likely that the speed in which you sew using the presser foot will affect these settings: I have had this happen a million times. Why are my stitches suddenly so small when I sew fast - aha! This is why. Mechanical machines are also heavy. This is one of the reasons I want to get rid of mine. Carrying them every week to class is starting to drive me crazy.
Electronic Machines are mechanical machines. This term appears to describe machines beginning in the 1970s. There is a technical description of the mechanics of an electronic machine vs a mechanical machine on The Ultimate Sew and Vac web site. This did not make it easier to understand for me, but it did explain things. Most dealers use both terms and I have come to the conclusion that they basically mean it is not computerized. The ones I like so far are the Husqvarna/Viking 118 and the Singer CG-590. There is a significant price difference - the Viking is $450 at my local shop and I can get the Singer online for $300.
Computerized machines have a microprocessor. These are the ones that have led screens and tons of fancy stitches. The ones I don't need, except it is not easy to find an inexpensive Electronic machine with the speed control feature. The main thing to know is that the lower end machines are not built with a protective interior case. These are basically cheaply made and intended for the sewer who makes a project once or twice a year. Not for me. A middle-end (is there such a thing? There must be if there are low and high ends!) are machines like Janome Magnolia 7330 and the Brother Innov-is 40 . Both of these machines run around $350-400 and neither are aesthetically appealing to me (I wish I could just get over that... but yuck!)
So that is where I am at right now. I had hoped to buy two machines for around $250 each, but I think that may be impossible. We'll see!