Being ca 70 cm long* I do not think the FC100 may be deemed "airline portable".
These small refractors show highly contrasted views, and can equalize or even outmatch a lot of larger telescopes if the seeing is acting as bottleneck (IME they are at their best when the maximum resolution is around 1 arcsec, i.e. 52Or can be split, but Zeta Boo can not).
If you have a seeing that consistently allows details close to 0.5< arcsec to be resolved, a 4" could turn rather disappointing, no matter how good it may be.
If you observe from sites haunted by a not so good seeing*, and most of times even 1 arcesc details (e.g. solar granulation, the 5 largest among Plato's craterlets, etc..) fail to be noticed, a fine, quick 4" refractor may gift you a lot of pleasant nights.
I have no direct experience of the AX103, but the vendor from which purchased the FC offered me it as a viable alternative for visual, and probably a better astrograph than the Tak
*larger telescopes will always show the same details, but in such cases the telescope with the better contrast will do it more easily (and quite often ,with the most pleasant look); the larger telescope may look a bit fuzzier because of the atmospheric flickering, allowing for instant pop up and sudden disappear of those smallest details the smaller one can not resolve
*may be shortened by unscrewing the dewshield and focuser, but in such case you will have to get some plugs to protect both ends.
Edited by Hesiod, 31 March 2016 - 06:34 AM.