There's currently no reason to believe Monero has hidden inflation. The range proof checks out. But it is possible, I'd say less possible than the trusted setup ritual in zcash being exploited, but sure, still possible.

As far as USD exchange rate, yes bitcoin outperforms it. But it still outperforms USD so far as a savings vehicle. You pick the best SoV you can, and Bitcoin is by far the best SoV, but if I'm going to engage in person to person commerce I want to keep my activity between myself and my counterparty. There's nothing out there that enables me to do that with the same guarantees and liquidity as Monero.