If I made a sorcerer with 18 STR. I would be just as good with a longsword as a fighter, but the fighter can attack more often? Is that what this boils down to?
If I'm understanding things correctly, yes as long as the fighter didn't have any weapon style that made them better at fighting with a longsword, such as Duellist. Plus, unless your sorceror was a race that had longsword proficiency (eg elf) they'd not get their proficiency bonus with anything except staves, daggers or light crossbows. And unless they invested in armour feats, at the expense of ones that might be more useful to them as sorcerors, they'd probably not want to be close enough to the enemy to stab them with a sword anyway! Though I guess that latter might be mitigated by use of some spells.
An as you say, it's a bit hard to know what difference feats would make over time until we get the full list that would be available, but I guess just thinking about Ability Score Increases alone is that, for a fighting class, you'd naturally be putting points into stats that are going to make them better over time, whereas if you did that for a sorceror then it would mean foregoing increases to CHA which is unlikely to be a good tradeoff.
