The Murray is crap, it isn’t worth carrying home for free.
The Giant might be okay, but you’d have to sit on it to make sure it would support you without sagging more than a quarter-inch or so (-generally, you want a air-bladder shock if you’re a heavier/larger rider, not a coil-over shock).
is a repeat of ad #1…
The Specialized Rockhopper might be worth having.
The Diamondback Cross Campus might be okay but it looks like a girls-sized bike–there is even a girl standing in one of the photos–and with the sloping top-tube, it’s probably a really small frame. If you’re 6"3" you likely won’t fit on it.
I’ve got a Specialized Rockhopper of about the same vintage and design, and I’m about 6’3" too. It cost me £500 (US$900) new at the time, though a similar bike today would be about £400 ($720). It’s a very well designed bike, tough, reasonably lightweight, and very responsive. And as it’s only got a 7-speed cassette the gears shift beautifully. I don’t feel the need to get rid of mine, and with constant maintenance it should last as long as I do. I’ve upgraded my main bike to a full bouncy Marin for proper cross-country mountain biking, but I still use the Specialized for popping to the shops or post-injury training. It’s a great bike.
Actually, the main advantages of the air shock are lighter weight and possibly more tunability rather than reliability. And then you’ll need a shock pump. Nothing at all wrong with a coil-over shock. Unless you’re what is perhaps unkindly referred to as a Clydesdale [read: tremendously heavy] rider, this could work for you. This looks like a single-pivot rear suspension, which is relatively uncomplicated. Giant is a good name in bikes. If it fits you, it could be a very comfortable bike to ride. I’m 5’6" and would probably ride a small or medium. This is probably too small for you. You should also be aware that A) full suspension makes for a heavier bike, and B) the manufacturer typically uses cheaper components somewhere to keep the price in check.
I didn’t see this one. Was it deleted? It would be uncomplicated and probably trouble-free.
It does say adult large. It seems small with the railing in the background, but it’s really difficult to judge from the picture. The sloping top tube is getting used in a lot of bikes of this type to increase standover height and isn’t just on smaller bikes anymore. But ditch the cable lock. You get almost zero protection from cables.
I think when I was last looking at full-suspension mountain bikes (perhaps 4-5 years ago) I weighed 230 lbs, and NONE of the coil-over bikes I found had a shock that was stout enough to sit properly with my weight, even adjusted to their preload limits. They all seemed to be built for a ~150 - 175 lb rider. For rear shocks that had maybe 2" of travel and were ideally supposed to sag about 1/4" normally, they all sagged at least halfway down. The air shocks on the other hand could be inflated enough to sit properly.
…It is true (or at least was back then) that the air-bladder shocks do get leaks and go flat–but if you’re heavy and you want suspension, the coil-overs usually won’t work at all for you unless maybe you get some specially-made super-heavy spring for them (if you can even do that).
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I suspect that
a) they really wanted to sell you a bike (duh!) and
b) they were overinflating the shock to show you the proper amount of sag.
An overinflated shock would probably leak air even more than a properly inflated shock. I think the oversized rider has some special challenges no matter what.
For heavy riders, there’s a few bikes on which one can mount use twin shocks side-by-side. The manufacturers don’t intend it or provide parts for it, but with some simpler hardware you can do it yourself.
-The one that was deleted, sold, apparently. It was a lower-end (plastic toe-clip cages) unsuspended Specialized Rockhopper.
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I would think that for a larger rider (6’3", even at ideal weight is pretty big in cycling terms), and for mostly just riding around town a bit, rear suspension is something that you emphatically don’t want. Just more things to go wrong, and rear suspension is really, really unnecessary for on-road or basic trail riding. That Rockhopper was the best one of the bunch for the OP’s purposes, I think, though it would depend somewhat on its condition - it was pretty old (pre-front suspension and SPD pedal days) and the components might have been getting pretty sloppy. The Rockhopper in those days was Specialized’s entry level mountain bike, and always had decent-but-not-great parts, pretty much exactly what’s called for in this case.