I agree. If it's between two companies that pay "competitive rates," and one company wants me to interview for an hour and one company wants me to interview for a day, I'm not going to waste a day.
If you were paying 2x rates or real equity, ya I'd slog through a day long interview, but I bet you aren't.
What does your company have to offer that would compel me to spend 8 hours interviewing that another company doesn't?