Apply with Capitol On Pre-Approval letter or Referral?

Does applying for a Capitol One Quicksilver card using a mailed pre-approval letter offer give increased chances of acceptance by Capitol One than a "refer a friend - get $150 bonus"

I have a good income, good credit, and a Capitol One card. My friend has no job, no credit (cards or otherwise - not BAD, just non-existent), but does have minor investment income.

He received a couple "pre-approved" mailers from Capitol One Quicksilver. I can send him a referral from my Capitol One account and get a $150 bonus if he is accepted using that bonus link.

If he applies online on their website and gets accepted, there is a $200 bonus for him (if $500 spend in first 3 months). If I refer him and he gets accepted, I get $150. If he uses the pre-approved mailer and gets accepted, he gets the card, but there are no bonuses.

Is he more likely to get the card if he applies from the Pre-Approved Mailer than the Referral Link?

I wouldn't want to send him a Referral Link to get the bonus to have him get denied when the Pre-Approved Mailer would have worked.