River vs Cashapp for very small DCA?

Im a complete beginner and I plan on setting up buying $12.50 automatically every week. I was wondering if I should use cash app or river since it’s such a small amount. I know after a week the buy fee will be $0 on river but they still have a transfer fee. While cashapp has the buy fee but no transfer fee if you use their standard transfer version. If I go with river, I would have to keep the bitcoin on their platform longer until I have enough to make the transfer fee worth it right?