I didn't notice any performance  difference between my 310 and my 310ET, but another thing to keep in mind with TECSUN and similar radios is they are not always consistent over time and from one set made at the same time as another. However, they still normally offer great value, even if they are a little unpredictable.

I greatly prefer having an antenna jack so I can easily access an antenna ground but I think I liked the 310 better than the 390 for other reasons too, but I don't remember what they were.

My opinion is of course just an opinion I am sure others would not share.

-FARMERIK