It makes the standard attribute array a little better, deciding ASIs a little easier, and might get you an extra feat you wouldn’t have gotten otherwise.
I’ve though about this a lot, and the only interesting difference I’ve come up with is that it takes some of the pressure off of deciding where to put your attribute scores.
For a typical spell caster, you have three important stats:
Constitution, which affects your hit points total, CON saves are very common, including saves against negative effects and most importantly, concentration saves.
Dexterity, which affects your armor class, and DEX saves are very common
Your spellcasting ability, which determines your spell save DC and spell attack modifier.
If we roll the first and third bullet points here into one, now we only have to worry about two of our attributes instead of three.
So instead of those three bullets getting (15,14,13) from the standard array, they now get (15,15,14) or (15,14,14) since constitution and Spellcasting ability get rolled together. So this is a little bit better at character creation than a typical spellcaster, at least in terms of strategically distributing your stats.
This pays off further as we level up. Once again, instead of having to decide what to do with three important stats, you’re only worried about two. And as you progress further, and you’ve got your two stats where you want them, you may be able to squeeze an extra feat out of one of your ASIs, since you aren’t worried about three different stats.