You will find that manufacturers aren't very generous on slope recommendations. It is important that you feel comfortable and in control. Part of that goes to how you feel in the seat and that you have a drive control that you are at ease using. I like hydros for that reason on slopes. Some tires are also better than others so that you stay in control.

your comment

"I would like a mower that can cut on a slope and not feel like the mower is going to turn over "

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review the owner manual of the mowers you are looking at. Usually the manufacturers of riders recommend limits on the slopes due to safety concerns involving turning over. Additionally recommendations are given to mow up and down the slopes - not across the slopes. The lighter duty riders have a lighter duty hydrostatic transmission and not not intended for steep slopes.

most of the mowers in the department stores and home improvement stores are lighter duty. The garden tractors have more durable transmissions.