Obviously I’m not neutral but here’s my two cents.
Variety is only important for protein to ensure you’re getting all the amino acids. Huel does this mainly with two protein sources, pea and brown rice, although oats and flaxseed provide minor amounts of protein. Increasing the number of protein sources without increasing the amount of protein offers no benefits.
The same is true for fats.
In regards to fibre, the fibre in Huel comes from the whole ingredients oats and flaxseed. Whereas Mana add the fibre as isolated ingredients. There’s no problem with either option but more variety e.g. adding carrot fibre, again is not adding any extra benefits.
The effects are very similar. As Adrián has said maltodextrin can provide a quick source of energy and is helpful for providing a smooth texture and easy processing, but not much else beyond that.
Both Huel and Mana have a low GI (below 55) but Huel v3.0 has a GI of 16 and Mana a GI of 29.