Rene's garden is also good for providing info, gardening tips and even recipes.
Dixondale is the best for onions.
But do remember that seed companies are in the business of selling seeds so they are going to tell you about their strengths and not so much about their issues.
There is also regional issues. Varieties that work in the North won't necessarily work well in the south or West. And each region or state may have climate, soil, pest, or diseases that seeds make some seeds more adaptable.
For specific plants, your local university extension site will have information about what grows best in your area and what kinds of resistance you need for the ones you choose.
For instance, I need nematode, CMV,TMV,fungal,bacterial wilt, rust, and heat resistance on most varieties of fruits and vegetables I grow if I am to get a decent crop. However, the trade off for that is often flavor and tenderness, so I have to find the best variety that tastes decent that I can grow.
A lot of that is experimental. I can grow Vidalia onions but they won't taste the same because I am not growing them under the same conditions as they would be growing in Georgia. I got a great tasting Brandywine, but it was not as big as it could have gotten and I had to prophetically spray it for fungal disease. Not to mention the birds ate half my tomatoes.
There are some places like Tatiana's tomato base and morningsun herb farm tomato taste tests that are a good place to start for tomatoes.
Happy gardening in Hawaii. Gardens are where people grow.