I prefer tortoise shell glasses.
But this question is more of a person choice.
Comparison of black and tortoise shell glasses
1. Someone who wears a pair of black glasses appears to be more professional and serious. People may feel they are more reliable in work, but sometimes they may be considered as dull and boring.
2. Someone who wears a pair of tortoise glasses appears to be more fashionable and in. This pattern gives you a very different look from others. You may look stylish and unusual.
In my opinion, I prefer the black glasses which are so popular this year. The color of black will be suitable with all other colors of the clothing or other things. In addition, the black glasses will look young. If you choose the big frame of the black glasses, you will look so fashionable and cool. I like the black glasses for its color and its shape.
Ok, I know both of the glasses you described. In my opinion , this is only a matter of personal taste. You cannot expect everybody to agree with you. And as to me, tortoise shell glasses are much better, for they are rarely seen compared with black ones, and you could appear to be more attractive and amazing. Try to get yourself a pair of tortoise shell glasses. at Amazon!
Personally I prefer black frames. I really love black and white. But I would also consider tortoise to match my clothes. If you feel hard to decide, you can use the Virtual Try-on System to apply your photo to see which is better for you.
Here is the link: https://www.firmoo.com/tryon/