It really depends on how you sheet the sail with your main sheet tackle.

Old style booms transfered the sheet load through the boom to the sail.

Most of the current sail designs use a strong gromet in the clew or webing sewn onto the leach of the sail at the clue.. The main sheet shackles to this point. The boom simply floats inside the webing. So... the boom's main job is to induce rotation of the mast and allow you to outhaul the sail.

You can now get away with a really light weight alluminum extusion... read cheap.. The down side is... If you stuff the boat and hit this lightweight boom... it will bend easily. Your new carbon boom will take more of a bump... hwoever, when it does fail... it won't bend... it will go boom!

On the A cat, the reason to go to a carbon boom is for the option of sheeting from the center of the boom of a large diameter and thus stiff carbon tube. There is not much advantage if you are rear sheeting (unless the boat is heavy)

The advantage of centering the sheeting point on the boat is that your pull is now inline with your body while on the wire... The sheet load is not across your body angled to the center of the traveler while you really want to be looking forward for puffs and waves. Besdes its much easier to pull this way for us old guys

Also, Make sure you manage the dissimilar materials when you put the fittings on.... they will deterioate rapidly and the new boom will give you no end of headache.

EG... be careful with a rivet... usually you want a backing washer gooped with the anticorrosive so that it doesn't deterioarte or pull through the carbon laminate when you pull the rivet.