Both are very good antennas. It was suggested to me before that the FPVLR is best if you are in an unobstructed or non urban / non suburban area and that the ITELITE is better in such areas. It may seem odd because bother are line of sight 'beam' antennas. What I have found is that the suggestion seems valid. In an area of 'clutter', that is a bunch of low buildings, the ITELITE seemed to give a bit more performance and in an open area such as rural the FPVLR worked as well, perhaps a little bit better.
I did not consider that either one was so much better than the other as to worry about it except at extremes.
The FPVLR antennas are "helical" type and the ITELITE are "patch" type or patch arrays. Patch and helical will both work with any type on the other end, except that helical antennas on both ends require the same 'handedness', that is, right hand or left hand spiral direction.
A guess at why the FPVLR had less subjective performance (subjective because I had no scientific way to measure it) in my tests could be that as the signals bounce off objects between the transmitter and the receiver, the rotating polarity of the FPVLR wave over distance means that at any specific distance the polarity of the wave may be anywhere in the 360 degree circle, and this causes the polarity of the reflections from objects at random points along the path to vary accordingly, and so they did not tend to always 'add' their strengths as much at the receiver but sometimes subtracted from each other, worst when the polarity was rotated 180 degrees from 'normal' as it would be 180 degrees out of phase with the direct signal. The reflections would not be strong enough to cancel out the main beam but would cause fluctuations in the received strength and therefor distance performance.
This is just a guess and/or opinion however and one should refer to a proper knowledge such as the book "Antennas" by John Daniel Kraus. I have the 2nd edition but there is a 3rd ed. now and so some bargains may be available on this otherwise rather costly book. No I don't have time to look it up so, sorry just an opinion on this question.
Here there are some paperback versions of this 920 page book for amazingly very low price.
https://www.amazon.com/Antennas-John-D-Kraus/dp/0071004823/