I think its always a good idea if you use your own models rather than tutorial models for your portfolio because it shows your own imagination to an extent.
But if your like me and have lots of tutorial pieces I think its fine to start off with. Maybe you can modify them to make your own. For example if done the ferrari tutorial from this site but i've add an interior, different alloys and some decals to make it look a bit different.
It would be good to hear what people in the industry think
I've only done one tutorial following the actual tutorial, I usually use the tutorial as a guide and make my own out of it, different blueprints or reference images, but use the video as a step by step guide to help me along the way.
I'm not quite sure how they'd feel towards using it in a show reel, they might suggest that you you give credit towards the person who made the tutorial though.
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