Never heard of the apex kit. I have diamond surfaced sharpening stones as well as ceramic steels assorted wet stones and files. The common thread is that none are tapes. To my mind tapes sounds like kissing cousin to sand paper. What is good about something as thinly bonded as tape or paper?
I guess you could view them as sandpaper- of course, we're talking 40,000 grit sandpaper.
Polishing tapes (and I use that phrase as a shorthand: we often mean paper, such as
Post-It notes with a compound, pre-fab mylar tapes with extremely fine grit, or even Nex-Care medical tape with compound) can be finer than any Japanese waterstone. In fact, it's sort of a hybrid between sharpening and stropping. Some abrasive compounds used with tape may be only 3 microns- vastly smaller than the finest waterstones you'll ever find. And of course, for a fraction of the cost.
Now diamonds...I have no use for them. They have a very sharp angular granular shapes that, while they can remove metal very quickly, create a really ugly scratch pattern that takes forever to buff out with waterstones. I won't use a diamond for anything except flattening my 'stones; for this they work exceptionally well. I keep a DMT Dia-Sharp on hand just for that purpose. But IMOHO they're a hamfisted approach to use on fine Japanese knives. Still, if you must have diamonds, Ben does have diamond plates for use with the EdgePro, although he advises they're greatly inferior to the waterstones included with the kit. The diamonds do cut slower but they also last longer, fwiw.
The EdgePro Apex was designed by a professional sharpener, and many professionals use the Apex (and the upgrade model, the "Pro"). It uses synthetic waterstones in conjuction with tapes on a glass or aluminum blank- and of course, anything that your inguinuity allows you to come up with. It
is hand sharpening, but it enables your stone passes to be made with virtually no error. I'm no nOOb to hand sharpening but I can't imagine equalling the precision I get with the Apex. It won't sharpen knives by itself- it needs a human hand and brain to run it. And it won't work magically, you still need to understand the 'wet rock' on a fundamental level, but it will take human frailty and physical error almost completely out of the mix.
This is not to denigrate your freehanding skills. Just bear in mind that not everyone has that skill, nor can they all aquire it. For example, my Dad is an old-school mountain man, very skilled in woodcraft, tracking, hunting, knife lore and freehand-sharpening. But the loss of one eye along with a myriad of other physical disabilities (including the destruction of this right shoulder) has made freehand sharpening nearly impossible nowadays. But the Apex allows him to bring his 50+ years of sharpening skill to bear while eliminating his main weakness- a lack of strength and coordination.
No single solution is ideal for everyone, but my decades of experience as a professional chef and knife junkie has persuaded me that the Edge Pro is "the real deal." I doubt anyone who gave it a chance would find it a useless tool.