Something I've noticed in D&D editions is the shift away from levels and your skill gained with them to proficiency based on ability scores. The earliest iterations of D&D didn't really use your ability scores except to give you an XP bonus. By 2e, your ability scores mattered, but they only affected your ability at the high end of things. 3e changed all that with standard ability scores that were completely uncapped. Whereas 2e topped out around 25 or so (IIRC), 3e introduced monsters with ability scores that were in the 30-40 range with PCs that could get similarly high numbers. For better or for worse (worse, IMO), everything was standardized into a bonus (or penalty) for every two points higher (or lower) than 10. 4e streamlined this system: everyone advanced at the same rate, so the fighter's attack bonus from leveling was the same as the wizard's. 5e is pushing this even further, in which there is almost no level bonus and that the raw ability score is the main determiner of effectiveness.
My question is: what style of system do you prefer and why?
4e is my favorite game so it's not terribly surprising I'd vote for that one. I think 4e made ability scores less important. You only needed one good score (and one halfway decent score, depending on build). In some cases (an Essentials thief, for instance) it hardly mattered what your secondary was. Essentials 1 suggested a thief make their secondary either Strength or Charisma (just like in the PH1) but for a one-shot where I played an E-thief I chose Wisdom instead.
For me, ability scores should play a big role when it comes to skills (I don't like the idea of simply making the highest level fighter the general, it should be going to someone with lots of Int and Charisma; in 4e terms a military officer is probably a warlord, not a fighter) but should play less of a role when it comes to combat. With appropriate feats you don't even need to use a class's key stat as its high stat. (In a one-shot, a fellow player played an eladrin knight, whose key stat was Strength. Needless to say, he played very strategically, as befitted a really smart warrior.)
It didn't bother me much that a wizard's attack bonus increased at the same rate as a fighter's. (Here's where ability scores played a key role in combat.) A fighter is going to have more Strength and a fighter talent bonus, plus he's doing to deal far more damage. A starting fighter's attack bonus could easily be +5 over a wizard's (when it comes to using a weapon). The wizard could literally go their entire career without ever using their dagger, given the way spells work. By tying the wizard spell attack bonus progression to that of the fighter's weapon attack bonus progression, it prevented situations where you might have a wizard whose spells always hit (when the fighter never hits) or whose spells never hit (when the fighter always hits). Even if it turned out both classes hit too much (or not enough) only one change is needed.
My main beef with D&D Next's bonded accuracy isn't that it "doesn't work" because I think it can be made to work. I don't like how saving throws work though, or how a class that uses Dexterity to boost AC will see their AC scale when no one else does. At higher levels, a rogue might never really need to worry about getting hit, but everyone else does, and that's not balanced. At any level (but worse at higher levels) a wizard can target a monster's obviously weak ability score. (I don't think it's metagaming to realize the fire giant who was grunting to himself before the battle started isn't that intelligent, and probably isn't all that agile either.) A level 1 wizard with Int 18 is looking at +4 vs -1, a 5 point swing. Not that 1st-level wizards should be facing "paragon"-level fire giants, but an at-level wizard won't find the fire giant to be any kind of threat. In 4e, you can also try to target a creature's weak defense, but at most that's giving you the equivalent of +2 (unless you're fighting zombies, who specifically have very bad NADs other than Fort). In addition, by using the better of two stats, it's quite possible to explain why a monster might not have a terrible NAD. (Said grunting fire giant will have a bad Reflex defense in any system from 3e onward, but he could have a dynamic presence - high Cha - and have a good Will defense. Or he might be a shaman - high Wisdom - and also have a good Will defense.)
One key reason for the change from 2e to 3e was to make point buy possible. Point buy wouldn't make sense with 2e and previous edition's weird ability score systems. (Alternity used something similar, but the point buy wasn't weighed, which IME was a bit problematic.) Even D&DN will not move backward on that topic. A system like D&DN, where ability scores are so important, just wouldn't work with 2e-style ability scores.
But overall I like 4e's system better than D&DN, because in 4e you can actually get better with non-combat skills over levels, but in D&DN you can't really. That's especially the case with, say, a warlord-archetype (probably a fighter with high mental stats rather than its own class) who can only really boost Strength because they want to be useful at combat and not
just be capable of leadership.