Honestly? I’m all for the thought that ‘beauty is in the eye of the beholder’ when it comes to art. More so, each and every person has different tastes, so it can be hard to say what exactly is ‘better’ about a piece. If your friends happen to think that way, I think they’re justified to their opinion. And I agree just as much with yours!

True, stylized art does take a matter of knowing about realistic anatomy/applications with your subject. To be able to create work with a style more loosely based off of real proportions while still being able to identify what it actually is is impressive and should be praised. 

But, being able to create more realistic are and recreate something from real life (or draw something in a way in which they’d probably appear in real life) is another thing. Because we see so much of real-life objects and subjects on a constant basis, it can actually be harder for us to achieve a more realistic recreation, as it is much easier to tell which details may be off.

But really, regardless or how much more ‘realistic’ or ‘toony’ your art happens to be, art is art. The style of a piece is one thing. Quality can be a whole ‘nother thing. 

And if art has to be judged for something, I feel it should be more based around quality, rather than the style, as there are factors that can be more factually discussed upon in that area (amount of shading necessary in an environment with certain lighting, what direction is the shading to be facing, perspective, etc.)

Ah, again, just my thoughts! However you happen to judge art is your business, though! There’s not always a ‘right/wrong’ reason!