The Experience 88 has a full sidewall layup, whereas the old Experience 83 has a blend of sidewall and cap. The 84 has a "Maxicap Sandwich" construction (i.e. sidewall underfoot blending into a cap construction for tip/tail) but with carbon in the mix as stated above. It's the full sidewall treatment that makes the 88 'more ski'. It has a more solid feel, it's more stiff in torsion and so has a smidge more grip, it has a bit more heft for pushing through crud, more damp, just more ski. I far and away prefer that solid feel of the 88 to the 83. I haven't tried the 84 yet, but with carbon in the mix I suspect I'll still prefer the 88. I'm 6'4" and 210 and I'd choose the 178 for my local hill, but would opt for the 186 in a larger, less crowded hill. The 186 needs more speed before it comes alive, and I don't get the opportunity to really open them up very often on our crowded slopes.
I agree with everything mentioned above. The Head Rev series is worth a demo - all the way up to the Rev 90. The Powertrack series is designed to be a one ski quiver and does the job pretty well. The Blister Gear guys wrote up a terrific review of the Powertrack 89 that comes to the same opinion (search it out). If someone told me I could only have one single ski I'd opt for the MX88, but the Kendo wouldn't be far behind, and the Experience 88 / Rev 85 Pro would both be thereabouts as well. The skis in Blizzard's flipcore series (like the Brahma) have a particular feel as a result of the rocker (negative camber) treatment. I prefer a more cambered ski, but they're worth a demo if only to get a sense of that feel.
In answer to an earlier question, your weight will allow you to flex a stiffer ski more easily than someone who is smaller, but selecting the correct length is important if you go down that path (as mentioned above).
Best of luck.