What each platform genuinely does well, and which one fits the loop you are preparing for. No platform wins every comparison, including this one.
Both give you real interview practice. They differ on anonymity, price per session, and whether the loop you are preparing for includes a machine coding round.
Pramp is free and peer-based. The trade-off is that your feedback quality depends entirely on who you were matched with that day.
Exponent is content-first and covers many role types. InstaMock is practice-first and goes deeper on software engineering loops.
Interview Kickstart is a structured, instructor-led programme with a price and time commitment to match. The question is whether you need the structure or just the practice.