Acer hd6810 VS Optoma UHD40

Hey Guys, I know these are older models, but I buy them used, and I want to know your opinion which one to choose.

I have a small cinema room in the basement with a 93 inch screen, and I must on the two above mentioned projectors. The room is dark, there are black (somewhat) echoproof panels on the ceiling, black curtains on the walls, and black carpet.

As I know the Acer have 3500 ANSI but the Optoma is only 2400. I really like Optoma, as I had a really reliable one before with (3200), but I'm afraid the 2400 ANSI lumens will be less enjoyable.

Also, the Acer have a 10,000:1 contrast, but the Optoma is 500,000:1, making it much better.

What is the math here?

3500 ANSI with 10,000:1

OR

2400 ANSI with 500,000:1?

Thank you in advance!