Well, I own all of the above, so I'll chime in on all of them!
First of all, for those who don't know what an interchangeable-type set is, it's a set of needles in a wide range of sizes, with which one can do nearly all of one's knitting. The short "needle tips" attach to a cable (various lengths are included) to make a circular needle. Any type of knitting, including regular "flat" knitting (like a scarf), or circular knitting, can be done on these needles. The kits offer convenience and affordability over buying dozens of individual circular needles (the kind with permanently attached cables), and far more flexibility than using ordinary straight needles.
Knitpicks Options set
The slick needle surface is very
smooth and luxurious.
This is, for many, enough reason to buy this particular set. And I knit with this set when I can, for this reason.
The cables are quite flexible.
The manufacturer allows for the set to be purchased in pieces, so you can try it out by purchasing a single size of needles and cable. Very nice option for the low-commitment new knitter, no other set offers this.
The set does not contain a reasonably short cable length. The shortest length is a 24" (measured from needle tip to needle tip), which is fine for some things, but compared to the 17" length of the Denise kit, this is a major limitation of the set. (See update below, some people are modifying their cables!)
Poorly organized kit. Needles are not labeled with their size, nor are the sleeves. It's very easy to loose track of parts of this kit.
This is my preferred kit when I'm knitting something flat, or large enough to fit on 24" needles.
Denise Interchangeable set
Available in our knittinghelp Store
Very practical for hats, baby clothes, and other circular items of such diameter. No other set has this short a length. I use this kit more than any other kit for this reason, and for the following reason.
Well-organized kit, makes it very easy to keep track of items and see if something in the kit is missing. This is a big deal for me, because I will grab my kit on the way out the door, and I like knowing if it has what I need in it.
Flexible cables. Even the 17" length is easy to maneuver, and literally easier on the wrists than most other sets are at their 20" lengths.
The most affordable set on the market.
Needle tips are warmer to the touch, and quiter sounding than metal tips.
Click-on needle tips are easier to attach and won't come unscrewed during knitting.
These easily pass through airport security, in my experience.
Resin/plastic materials are durable but less "luxurious" than other materials like bamboo, and even metal.
Resin needle tips are smoother than bamboo, but not as smooth as metal.
This kit is not luxurious, but rates #1 for practicality. When I need a 17" needle length, which seems like half the time, I use this kit. Also, if I'm going to start a project while out of the house, I grab this kit because I can tell if it contains the needle sizes I need.
Better organization than the Options set. I love the streamline case and the color-coded needles are pretty and easy to keep track of. Slick, metal needles (not as slick as Options, but second best). My only complaint about this set is the stiff cables. I won't use the 20" length, only the 24" or longer. Stiff means that the knitting flows along the cable smoothly, but it's harder on the wrist at that short length. The other main complaint about this set is that the needle tips come unscrewed, but that is easily remedied: discard their white rubber grip, and use a circle cut from a yellow dishwashing glove instead.
Webs Bamboo Set
Beatiful set with lovely bamboo needles. As with the Boye set, the stiff cable is my main complaint. I find the short 20" too stiff, but use the longer lengths.
Update--My own dream kit:
One day I'm going to do actually do this...
Shorten one of the Options cables to an 18" length, using heavy duty glue. I've heard some have done this. (Pull the cable out of the metal end, cut it, and glue it back in with 2-ton epoxy!)
I'll then take the needles and cables from the Knitpick's Options kit, and stuff them into my Boye Needlemaster case. This dream kit has it all: flexible cables, a short cable length, slick needles, and excellent organization in a streamline case. I can't imagine a more perfect kit, unless the Options needles were colored like the Boye set, so pretty.
Note about broken parts
All of the above manufacturers are good about replacing broken or poorly made parts. Broken cables, parts that don't screw in properly...these things are quite common in all sets, so don't judge the manufacturer on that...just contact them for replacement parts. They're all good at replacing parts.