All good points. The other piece of it is, should you start off with a very stable craft (V-8, etc.), and decide to move to an intermediate boat, you have two very strong options: keep the stable boat in your quiver for really big days, or sell it (There always seems to be a market for used entry level skis, particularly the V-8s, at least where I am.)
Coming from FSKs, I started off in what was then, a very tippy boat for me: a Custom Kayaks Mark 1. I was frustrated much of the time in bumpy water, greatly improving upon my swimming skills. Gave up surfski for a bit and went back to FSKs, then had another go with an XT, and immediately after that, an S1-R. The progression up through the ranks was for me, necessary. (Much later, bought their Synergy Lite and had a blast, once skills rose commensurately...) I still keep the S1-R and now, a V-8, just to purely have fun, or for winter paddles when conditions kick up, in addition to my elite boat. As noted, having a stable platform also allows you to develop proper form. White-knuckled brace strokes really don't do much for forward momentum.
Some folks are able to start out with an intermediate/stable elite boat boat and stay with it, but I'd say they're the exception, rather than the rule, particularly if they're not paddling with groups that will coach them along/support their acquisition of skills. Have one friend who jumped right into a V10L from sea kayaks and swam so frequently, his remount skills were legendary-still he stayed with it. He just bought a new V10 Sport and is happier than a pig to slops (Or for our Brit friends: 'a dog at broth.'). He's faster in everything, and stable, stable, stable. He battled the ego thing for quite a while; once he relinquished this, his fun factor increased considerably.
I'd also recommend buying used to start, as if you do decide to make an immediate upgrade, it's pretty much a turnover to the next boat. Cheers.