You're not comparing two treks.

We can show you the numbers, but we'd be doing you a disservice if we didn't say this first: Prashar Lake Trek and Vasuki Tal Trek - Kedarnath are not alternatives — they are different sports. One is a 2-day experience reaching 8,950ft, the other is 5 days reaching 15,300ft. If you're choosing between these two, one of them likely isn't an option for you yet.