Why traders run both
Only from this page: the $400,000 ceiling becomes $800,000.
Every ITAfx trader is capped at $400,000 in simulated capital across accounts, Terms §7(h). Accounts added from this page are the only exception: Instant PRO added here extends your ceiling up to $800,000, and that extension is not sold anywhere else. A second account is how you get there, and running two different rule sets is the point of it.
Your Instant on Demand account is built for frequent, spread-out trading: it pays on demand, with no payout day and no waiting room. Instant PRO is built for the trades that account cannot take: positions held through Friday close, and months where one day carries the result.
Trading is risk. Both accounts can breach and neither one guarantees a payout. What a second account changes is the range of setups you are allowed to take without breaking a rule.