Kung Hei Fat Choi girls! Wishing you all good health, happiness and success!and oh, Happy hearts day too!******************I borrowed my sister's fluidline to make a comparison.Hope you find this post useful.

PACKAGING :
Both are made of glass jars.
WEIGHT :
MAC - 3 grams
Maybelline - 2.8 grams
TEXTURE : MAC is a bit creamier than Maybelline.COLOR - PAY OFF :Same intense black color.
(click images to zoom) 
STAYING POWER :
(On bare hands without primer)
After a few minutes upon application, I rubbed it several times - it didn't budge or smudge!
When I placed my hand under running water and rubbed it twice, both liners smudged.
Maybelline smudged more than MAC, but hey- just a little bit!
See pic below.

TIPS:
Make sure to tightly close the jar after opening to prevent gel eyeliners from drying fast.
Other gel eyeliners I've tried:
Fanny Serrano gel eyeliner - dries easily after a month. Flaky texture.
Elianto gel eyeliner - creamy consistency at first. Dries easily too, making it difficult to use.
FINAL THOUGHTS:
Blacktrack is a nice gel eyeliner, but if you want to save a few bucks I really recommend Maybelline! Its a dupe of MAC Fluidline IMO. I've had this for more than a month the texture is still creamy.
Till next time,