Over the years, I've tried tile, slate, AstroTurf, shelf liner, peel & stick tile, vinyl fabric, and now linoleum.
I think I like linoleum the best. I bought a 6 foot by 8 foot rectangle from my local Home Depot for $24.99 plus tax (US dollars) and cut it in to 6 pieces for 40 gallon tanks and 2 pieces for 55 gallon tanks. So about $3.50 a tank/piece.
I use clear packing tape to stick it to the bottom of the tank so it doesn't slide around. When there is poop, I take a flushable wipe to clean up the poop and then I flush it. I never ever throw away poop-- it stinks!!! Flushing smells better.
I buy whichever brand is cheapest for me. The last box I bought was from Costco and was a Kleenex brand that had an instant store coupon.
The goal for substrate is a solid surface that is easiest for you to clean. Today I swapped out my old pieces of linoleum for a new piece. I took the old pieces outside and scrubbed them down good. Those are now in storage for the next empty tank or the next time I swap out all the tank pieces.