Won't be a fair comparison as such as my elgrand was higher milage.
Interior:
Alphard interior quality feels of higher standard
Elgrand had more cubby holes
Elgrand middle row seats swivel so maybe bit more practical fittin large items
Drive:
Alphard rode really, well even better than many Mercedes. Smooth power delivery and plenty of grunt.
Elgrand was XL model and I found the OEM suspension very floaty. Sold it and buyer said is very comfy. Each to their own I guess.
Fitted tein basis Z and ride was better if a little on hard side for a family car.
Didn't have any normal day to day issues with it and was reliable. 120000 miles on clock.
I find the elgrand a more utility vehicle as more flexible and easier to find roof racks, tow bars, uprated suspension etc
Aphard to me feels more of a "pure" people mover as harder/ more expensive to buy above mentioned accessories
If anything specific you'd like to know let me know 😊