Open table vs. RESY vs. other

Hi! I just took a FOH manager position at a small (13 tables inside and 8 outside) restaurant. Currently we take reservations for parties bigger than 6 and just stick them in good old Google Calendar. We also have a policy of taking a $25 per head deposit (via square) when the reservation is made and then that amount gets subtracted from the final bill when they arrive.

It sucks. Discounting the bill makes the final total significantly less and people tip on the discounted amount. Guests also find the process tedious and tacky. At my other restaurants we used either resy or open table and anyone can make a reservation no matter the party size and the system just holds your card to charge if you don't show up. I want to suggest changing systems but would like to hear everyone's thoughts on which system would be best/why. Thanks!