AT&T stock S3: Would a custom ROM give a large performance boost?

[Special K]

I'm using a Galaxy S3 using the AT&T stock 4.4.2 configuration. The performance overall seems sluggish. I've already gone through the usual checklist of deleting/disabling unused apps and files (except for the built-in ones as I don't have root).

Would installing a custom ROM and/or rooting give a large performance increase? I'd rather not go through the hassle if the only major improvements are to the UI.

 

[daffyducknj]

I'm currently using AICP (Marshmallow) on my Sprint S3. Yes, it is a much smoother UI, but it runs well, partly because it isn't as bloated as the stock ROM. There are also performance tweaks to the kernel it uses, as well as other software parts. On mine, it runs at stock CPU speed. I don't feel the need to have my device overclocked. I don't know if there's a build for the AT&T model, you'll have to look that up. Hopefully someone else here is using AICP for an AT&T S3.