So I have recently begun travelling quite a bit for work and have been using my cards to get max points. However, I'm having quite some trouble figuring out how to use my cards.

Here is how I normally travel.
Flight: Delta
Hotel: Marriott (Switched in September from Hilton)
Car: Hertz

Here are the cards I have:
Marriott Chase
Citi Hilton
Amex Platinum
Amex Delta Gold
Chase Sapphire Preferred (Just got this one)

So how would you use the cards? I am almost thinking of cancelling the Delta Amex and not using the Platinum for anything other than Lounge access. I think I will use the Marriott Chase for Hotel, Chase for Flights, Food, and Car Rentals.

Any thoughts?

Also, I wouldn't be opposed to switching to United as my main airline.

Thanks,
Pat