Is there any performance difference between iFlight's XING-E and XING lines of motors? I know that the XING motors have some better materials like titanium shafts but are there any performance differences?
The Xing and Xing-E motors have two primary differences, materials used in the bell construction, and the magnets used. The bell is a lower stength 6061 aluminum alloy than what they claim for the Xing primary line. Also, even though all motors tend to claim "N52SH" or "N52H" magnets in their specifications, there is a huge range of variation in magnet strength between brands and lines. The magnets in the E series appear to be a bit thinner than the standard line counterparts, but likely they are a tier lower in rating. The full Xing line also has either a two piece or single piece (machined as part of the top of the bell) aluminum cover surrounding the flux ring, depending on which version and when you purchased it. As you mentioned the Xing motors have a titanium alloy shaft while the Xing-E have a hardened steel shaft.
As far as performance differences go, yes there will be a performance difference. Differences in magnet strength and manufacturing tolerances mean the Xing line has more torque and higher thrust than the Xing-E motors. The difference is not going to be drastic however. The Xing were fairly conservative, coming in a bit under the stated Kv. I haven't tested the Xing-E in the bench yet, but I have done a few builds for friends with them and had them up close to compare.
Check out the details on the Xing here: https://www.miniquadtestbench.com/iflight-xing-2306-2450kv.html
I'll try to borrow a spare Xing-E from my friend who I did a build for and see if I can get it for comparative data. I'll update here if I can get it.