I wouldn't consider either of those modifiers to be particularly important.
If you're playing tall you want prussia/russia-tier military quality or quantity bonuses and -dev cost. If you're playing wide you want -coring cost, -WS cost, -AE, stuff like that.
All of the majors seem to be getting stupidly, ridiculously OP buffs elsewhere though, like England being able to choose what their colonies produce (including gold), Russia getting massive buffs from serfdom, and other bs.
They've also got coring, infantry combat(admittedly a mediocre bonus), and discipline. Improve relations and a massive manpower boost are also big.
They are on the same tier as Ottomans now. Discipline, Core Cost, swap cav for inf combat ability. And Ottomans have trash ideas like tax modifier and trade power. And the ultimate trash ability, -10% war exhaustion reduction cost. I remember the old days of Kebab -33% core cost. Now their 20% is lower than some nations. Every Angevin idea is good except maybe legitimacy. At least they don't have trash like -10% ship cost like Ottomans.
That is after controlling both France and Britain. This is kind of the equivalent of forming Italy, which has even better modifiers.
Italy has a lot more dead ideas as well as several identical ideas that are slightly better. I prefer Legitimacy over Prestige in ideas so Angevin wins that one. Italy has Stab Cost and Fort Defense which are both trash.
Of their remaining different ideas Angevin has Discipline and Separatism and +1 Parliament issues while Italy has Galley Cost and Galley Combat Ability plus Global Trade Power. Much rather be Angevin here.
They've both got +15% National Tax Modifier.
Italy gets +5% more CCC and ICA in their respective ideas sure. They also have +33% vs +20% on National Manpower Modifier. Italy has +50% Improve Relations vs +30% for Angevin. So they certainly win by having 4 higher value identical modifiers. But then we finally get to +50% Heir Chance and -10 Years Of PU Integration. And +15% GC modifier which is very good. Since England probably pushes for Economic Hegemon their GC value is insane. Of course Military Hegemon is strong as hell but still.
Once you literally possess Mare Nostrum, as opposed to just the Italian idea, Gally bonuses don't matter. The cost modifier is always 100% useless but you don't even care about the combat modifier after you control the whole Med. So functionally Italy has 3 dead ideas by the mid game.
Roman Ideas are objectively superior to Italian ones anyways.