WHMCS mod or cPanel mod?

Hi -

We have a free-standing PHP application (about 10 pages) that our clients use to manage databases.

We want to integrate this app into either cPanel or WHMCS.

WHMCS seems the simpler route.

But I don't want the overhead (and potential security issues) of having clients being logged into our portal for long stretches performing database operations.

Does anyone have any input based on experience on the relative merits (technical, customer service, etc...) of WHMCS integration vs cPanel integration?

I know it is a broad question, but if anyone has experience with both I would be interested in any feedback.

Thanks.