now see i could beleive that if we ever saw Ahsoka interacting or even near Shaak Ti but we dont even get an episode or even a naration oof the two interacting. i do think the Ahsoka illusion was a real version of Ahsoka the way the Qui-Gon aperision was real. If she had asked for a different master imediatly after Mortis or more specifically if she was assigned as Obi-wans padawan i think that is what she had the potential to become. but back onto the mater at hand.
i will agree with you on the fact that the tips of their Montral and the tips of their front Lekku pattern wise look the same, but the back and middle of Ahsoka's Lekku are completely different from Shaak Ti’s as seen in the profile right images. the only difference in horn shape is the tips of Shaak Ti’s curve outwards similar to bike handles.
its most noticeable in the profile view that the horns are different with Ahsoka's being more vertical and only slightly curved, and Shaak Ti’s being at a much more significant slope and being much thicker compared to Ahsoka's especially closer to the skull.
again shape is very similar but pattern wise they are very different. Shaak Ti’s patterning it much more horizontal and from the looks of it they are all equally spaced out. the top of Ahsokas horn patterning is curved towards to tip od her horns, while the ones on her Lekku are curved down and spaced out more then the ones on her horns.
Their back Lek are significantly different especially the patterning and Ahsokas front Lekku are longer then her back where as Shaak Ti is about equal in length.
compared to her “Potential” self and the model they chose to go with for rebeles you could honeltly think it was a different character all together if the facial markings were different. there is literally nothing i can say to compare the two in a detailed manner the way i did above. they are...just so different.
Below are just sketches i did of each iteration of Ahsoka Montral including concept art and the intended model for seasons 6 and 7
TOP ROW: The Clone Wars, Rebels, Rebels concept art, TCW S6 Model(used in S7)
BOTTOM ROW: The Mandolorian, Mandolorian concept art, TCW S7 Model
(wow it took me a long time to respond how fast a year goes by and this is just a fun analyst no intent for an argument.)