This summary review is hopefully going to be a little bit like the story of Goldilocks and the three bears. As in: small, big, just right. I currently have in my possession a Squirt and a Core, and have a Juice in the mail. I'll add more reviewage for the last one when it arrives.
The Squirt P4 was the one I picked up first, as it was reasonably priced as these things go. Which isn't particularly... but I was impressed enough with the solidness of this ~2 inch minitool to look further. I picked it up with the intent of putting it with flash drives and USB bits in my computer toolkit, as it's small enough to work in tight spaces inside a case. The main selling points for this application are small pliers and a flat philips screwdriver, plus an extra-narrow flathead that should fit many screwthreads on glasses. Also included are an awl (potentially useful if you need to sink a screw and have no other tools available, or want to clean your nails), knife and file. The sharpest edge on the outside is the lanyard ring, so it's entirely suitable for putting on a keyring — 50g is nothing, really.
The Squirt's also available with scissors instead of pliers (the S4) or electrical pliers that have a small gripping area at the tip and several sizes of wire trimmer the length of the plier blade (the E4)... if you're happy with a smaller gripping area, you may be able to get an E4 cheaper than other models — maybe not, as it isn't especially common despite relative unpopularity, or if happy to dispense with pliers entirely a Micra is probably going to be cheaper than an S4. It's not surprising Leatherman never released a Micra with pliers, as it would've cannibalised their market on more expensive tools.
What surprised me, even expecting it after reading reviews, is the density and precision of manufacturing compared to similar off-brand examples. All three models reviewed here also have a main blade manufactured in 420HC steel, which just means it tries to strike a balance between not rusting, holding an edge and being practical to sharpen. Not having to unfold the pliers to get at the screwdrivers and other tools is an especially nice piece of design work.
The Core was an accident. I bought a Kick, the entry-level 'fullsize' Leatherman, for a nice amount less than retail price. What arrived was a Core. Having checked with the seller, I'm keeping it, although I may find a better owner for it in the long run. It's the kind of thing a lot of people who use tools quite heavily on a daily basis would be happy with... hefty, all tools fully locking (with see-saw design buttons to depress to release them) and large. The size makes it a reasonable proposition for use whilst wearing work gloves, and the tool complement including a sheeps-foot serrated blade in addition to the normal one and a saw suggests an outdoors-type target market. If this includes you, be warned that by most reports the steel in these things is stainless but optimised for strength rather than resistance to corrosion and regular cleaning is advised.
A possible downside is that the Core doesn't have a bit driver you can change the screw heads in. Weighed against that is a decent (twenty-five year) guarantee on parts, plus the ease of losing separate parts and fact that Leatherman don't use industry-standard bits anyway. Heavy screwdriver users are better off with separate tools in any case; the amount of torque achieveable with a multitool is always going to be limited, plus you can get a wrench around a screwdriver or feel okay about hitting it with a hammer to loosen things...
So, not a bad thing to have in the house/car for emergencies, but a bit much for my needs. Rather than go back to the Kick, I've settled on the Juice C2 as potential best candidate for a general tool. This is in spite of them being viciously overpriced for the size, with a typical pricetag not far off premium models such as a Wave or Skeletool, and even half-price deals feeling high... but really, the same goes for Squirts — if you can't get them under half, odds are you're going to feel a bit ripped off.
This particular model of Juice substitutes a corkscrew instead of scissors. Since something people in my company seem to be looking for a lot and assume most multitools have (they don't) is a corkscrew, and since I haven't used folding scissors since I was in secondary school, this is a plus. The default colour of red is nicely retro — folded it's basically a Tim's-story-come-full-circle swiss army knife, except with the incredibly useful addition of pliers. Not looking like a multitool and not being plain steel also means people are a bit less likely to suffer from surprised brainfarts when you offer them something to cut packaging with.
There are some obvious downsides, even before it turns up: the design isn't as convenient as the Squirt, because the screwdrivers unfold from inside. Aluminium is a fairly soft metal to use for exteriors which'll scratch over time. And, as indicated before, you can easily pick up a good fullsize tool for the price of a pocket one.
As for actual usage... despite having a basic complement of tools, the C2 doesn't feel too light. Being one of the two thinnest Juice models the pliers are off-centre, and they have a bit of flex in the handles when gripped tightly. The blade also has some sideways flex which accompanies a rather skinny "orange segment" build probably best suited to fruit, though doubtless it's still fine for most things I might use it for. However, the flat-head screwdrivers are a singularly dubious bit of design. As supplied new they have a lot of resistance to being pulled out, and I've already joined other reviewers in gashing myself on the middle screwdriver. They're fine on used models I've had access to.
The Juice is available with scissors instead of corkscrew (S2), various sharp things and file (the discontinued KF4), corkscrew and scissors plus a saw (CS4), everything (XE6), or everything plus a foil cutter and tweezers (the pretty rare Pro model.) The numbers stand for how many external tools are available on the model. Needless to say, they're less common and tend to go for more than well-specified fullsize tools such as the Wave unless you get lucky. Speaking of which, the CS4 is a generally more balanced piece (even if you won't use the scissors)... the pliers are centred, heft good and overall weight is still pocket-friendly — almost like a big version of the Squirt. Recommended.