I suppose the biggest reason to consider changing is benchmarks.
I've attached two here, the first is a connection benchmark. Zap time is far better on XUI, but the main cause for comparison would be how well each piece of software handles simultaneous connections. In order to test this I disabled all flood limits and nginx rate limiting and set up a siege attack against two 8 core Hetzner VPS's (CPX41 server). The parameters of the attack were to send 1000 requests per second to a valid stream URL on an unlimited line, so it would have to check the line credentials, whether the stream ID exists, if the stream is online, figure out load balancing, check if the stream is in the allowed bouquets then redirect the client to the load balancer, once there it would need to generate a HLS M3U8 and then exit.
XC 2.9.3 buckled under the pressure of having to do this and pinned the CPU at basically 100%, XUI 1.4.1 beta (latest) averaged around 17% CPU with caching turned on (default).
Benchmark 2 is a real world comparison of online streams and online connections performed many months ago on a legacy XUI version (1.0.13), versus StreamCreed 1.0.1. Since then there have been 27 full releases of XUI to bring us to v1.4.1, so the benchmark is very outdated and XUI has come a long way in terms of speed too so the performance difference would be even more severe now. Both results are from the exact same server.
As you can see, StreamCreed was at around 84% CPU usage at 3,600 connections and 500 streams. XUI was around 50% CPU usage and 60% RAM usage at 7,000 connections and 750 streams. Extrapolating the results XUI is 226% more efficient on CPU and 176% more efficient with RAM.
Your mileage may vary of course, but this is a real world scenario from a client who knows what he's doing.
So yeah, you get the odd moron saying IT'S THE SAME SOFTWARE, but look a little deeper and stop being so superficial.
As there seems to be some interest, I'll open XUI up for trials soon.
And for those who wonder what changes have been made, changelog is here:
CHANGELOG