Your question is a little tough only because there are so many different choices and manufactures.
For instance, 0.35 or 0.45 wire can be used with CO.2 or CO.2 and Argon Mix and establish Low Hydrogen strentgh.
Now when it comes to Flux core wire's you have a huge spectrum to choose from. Inershield is one choice that is Fluxcore that is normally used on much larger projects that require 3/8 1/2 3/4 and 1" weld sizes
Pagewire has a 0.35 and 0.45 flux core wire all have different flux make up's that raise the tensile strength.
My suggestion is to check with your local Welding Gas Distributer that normally have all the information and chices from many suppliers and you can make an informed decision.