The distinction between the two methods of distribution becomes less important over time though.
Assuming in a year or two both systems have distributed 50%+ of total posible units (already true of Bitcoin), how will they differ afterwards ?
Bitcoin will continue small incremental distributions effectively indefinitely while Ripple will have that 50% "Fort Knox" stash in the background.
At that point various scalability issues in Bitcoin (TPS ceiling, blockchain size, etc) will be contrasted against scalability strengths of Ripple, while Ripple's Systemic Risk will be contrasted against Bitcoin's lack of centralization (although such centralization is still possible and maybe even likely since a large enough "printer" or just a large bank can attempt to corner the Bitcoin market, i.e. compare to how Silver market is effectively cornered and suppressed today).
I speculate that two different uses will be found, very high transaction rates and trading volumes of various assets against each other and against XRPs in Ripple, but I don't see many people feeling comfortable storing too much value in XRPs over long periods of time,
because of ever-present possibility of the XRP flood from the "Ripple Fort Knox"
In either system, there is no long term way to sustain the ceiling for too long tho, although, ironically, Ripple enabling massive BTC IOU issuance by fractional reserve gateways might create a "paper BTC market" 100x of times the actual size of the "real BTC market" again, similar to Silver today in which case Bitcoin can become as tamed as Silver or Gold are today.