Sharing real world usage stories is often more helpful than any advertisement. For light summer tops I keep to my normal size to avoid a baggy look. I think this is one of the few real advantages we have compared to shopping blindly. Many times I avoided a bad purchase just by reading a few careful comments. Sometimes one good quality item is better than five very cheap ones.

If anyone is interested in real user experiences, I sometimes write short notes about the shops I test.
You can find one of the pages here:
[url=http://avia-bookjans.de/index.php/component/k2/itemlist/user/47843]
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Some care only about style, others focus on comfort and durability. Metal can feel more premium, but acetate can be more comfortable for long wear. For example, I compared cotton, polyester and mixed fabrics for similar clothing items. I like when they mention whether the fabric has stretch or not, that detail matters a lot. Nose pads that are too hard leave marks and feel uncomfortable on the skin. For light summer tops I keep to my normal size to avoid a baggy look.

Hope this helps someone.