People can and will over complicate this one. It really is simple. The things to verify first are
1) is your scope truly level? If not, both methods will not be accurate
2) does your turret move the amount it says it moves?
Many scopes aren't true 1/4moa or 1/2moa adjustments, but are a small amount off. Over time, dialing up and down will change your zero because it doesn't go back to the exact same spot it did. So, test it out by shooting a few squares. Set a target at 100, shoot the center. Dial up and over to the corner and shoot, then work your way around the target corners, coming back and shooting again in the center. See if your POI has changed with adjusting the turrets. It helps to do this at exactly 100 yds and on a grid target so you know how many clicks you need to move to the corner.
In a hunting situation, holdover is faster but dialing is more accurate if you're not perfectly level. A heavily canted scope using holdover will usually mean a miss by a wider margin than a canter scope that's been dialed.
If you're going to dial, dial it all. There's no reason to do 2 in the turret and 1/2 in the reticle. Most turrets are 1/4 moa, so dial it for exactly what you need a hold dead on.
In your example, if you wanna hold over 2.5 moa and you have stadia at 2 and 4, honestly eyeball the gap for that extra .5 moa. Don't dial it. Your brain should be able to parse that gap into quarters and make a reasonable estimate of where 2.5 moa will be