I had some questions and requests for photos, so I dug around in my archives (good grief) and found some decent shots of the styles under discussion. I'll also try to give a better explanation of what I mean by seamless vs. sorta seamless.
The first three yoke types I mentioned, raglan, saddle shoulder, and circular yoke, are all variations unvented (her word) by Elizabeth Zimmerman. There's a fourth style I forgot to mention last time, the box-the-compass yoke. It's halfway between a raglan and a circular yoke, creating an octagonal stripe around the neck instead of a circular one like in a yoke, or a square one in a raglan. All but box-the-compass methods are explained in "Knitting without Tears" by Elizabeth Zimmerman. The box-the-compass is found in "Meg Swansen's Knitting".
All four of these sweaters are knit the same way: You knit the body and arms up to the arm pits, join it all together, then do some sort of decreasing (therin is the only difference in these styles), up to the neck where some sort of hem or ribbing is made and then the whole thing is bound off. All that's left are some stitches at the arm pit to graft together. (It depends on the gauge and the size of the sweater, but in reasonable sizes and gauges, it's about fifteen or twenty stitches.)That's it. The end. No other fussing. I guess if we're getting really technical I should be calling these 'no fuss seamless' or something. Anyway, here are the different types. (Other than box-the-compass, because I've never knit one, but it's VERY similar to the yoke style.)
As you can see, there are four decrease points, directly above where the sleeve meets the body on each round. This is (in my opinion) the easiest of the three styles I'm showing here, and is flattering to nearly everyone. I've heard very thin women with broad shoulders complain that raglan shoulders aren't flattering, but to be honest, I've never seen anyone look bad in one of these. Mind you, this style is meant to be loose and casual; you start doing a tailored fit, and while it still may look good, it's going to be a lot more trouble.
Whether you believe it or not, this method of decreasing is very similar to the raglan. Instead of diagonal lines of decreases, the decreasing is fudged to give straight vertical seams, with a shoulder strap across the top. With little fuss, you can do fun things like run a cable up the arm and across the strap:
In terms of knitting skill, I'd say this is the hardest of the styles, but in terms of math, and figuring out the percentages and doing the pattern from scratch, this is as easy as the raglan is. Which is to say, very.
It's thought this style was invented by Bohus Stickning, to show off beautiful color combinations like the one shown above (which is taken straight off one of their patterns, the Blue Shimmer). If you were to knit one of these babies in one color (though I don't know why you would), the knitting skills required would be on par with the raglan - very simple. However. If you're doing stranded color, or writing your own pattern using the percentage system, or BOTH, it can get complex fast. I re-wrote the pattern for the sweater shown above, and found myself doing stuff like "increase by 25% to a number of stitches divisible by 12". (The divisible by stuff was so that I could fit entire pattern repeats onto the yoke.) So the math is pretty involved. Not hard, it's still middle-school level math skill, but it's certainly more elaborate than the raglan or saddle-shoulder.
The box-the-compass yoke is a sort of hybrid between raglan and circular yoke; it has stacked decreases in columns, like the raglan does, but instead of four columns, there are eight. Looks kind of cool, but the math is as elaborate as the circular yoke, if not moreso. (I was considering this yoke for the Zen sweater, until I looked at the math involved and thought 'that's not Zen, that's math'.)
This brings us to what I think of as 'semi-seamless'. There are literally dozens of variations on the theme, but ultimately what it comes down to is knitting the body as one big tube, either steeking the arm holes or knitting the back and front flat (oh yeah, two-color knitting in purl, VERY zen. Not), then joining the shoulders. Usually a three-needle bindoff is used for the shoulders, but there are other decorative methods and grafting is also done. Then, the sleeves are either knit from the cuff up and grafted into the body (or sewn or several other even more complicated techniques similar to a three-needle bindoff), or else sleeve stitches are picked up around the arm hole and knit downward, dragging the entire sweater around and around and around on gradually faster/shorter rounds.
Yes, technically, these sweaters are seamless. From a purely structural viewpoint there are no seams. However. Once you've grafted in a sleeve, you'll be sure it FEELS like sewing the damn thing together. And while picking up the sleeve and knitting downward is no-sew/graft, by the time you get to the wrist of the second sleeve, you'll feel like all you've done is twist the sweater in a circle over and over for half your life. Not to mention, if you're really nit-picky, the pick-up-and-knit-down throws off the pattern no matter what you do, because the body of the sweater is knit UPWARD, and the sleeves are knit DOWNWARD. (Unless you're knitting from the neck down, but that's another issue for another post.)
I've knit lots of sweaters this way, and this method accounts for the vast majority of traditional European knitting, including Norwegian and Fair-Isle. Here's a Dale of Norway to illustrate the point:
This baby was knit upward, with steeked arm holes and a three-needle bindoff across the shoulders. I then knit the sleeves from the wrist up (so that the 'lice' on the body matched the 'lice' on the sleeves) and grafted the sleeves into the body after cutting the steeks. (I also steeked the neck opening.) Again, while this sweater is technically seamless, I spent as much time doing finishing (mostly grafting) as I have on seamed sweaters. Really the difference is a technical/structural one, not method/time spent.
There you go. More than you ever wanted to know. Now go knit your own. Ohhhhhm.