They will feel and perform similarly since they have the same switch type. The HyperX Alloy Elite has slightly better build quality. I have heard that the Strix Flare has firmware issues.
I would just get whichever one looks better, but my (very slightly favored) choice would be the HyperX Alloy Elite. If you have like anything that syncs up with Aura Sync, it would be better to get the Strix Flare just to color match.