It really depends ... If you are talking about pure Domain Speculation - I'd prefer an Ovt Monthly Search to be somewhat consistent in the 100,000 and Above Range. And of course Everyone would prefer the .com Version / Extension (Not possible most of the time) If it is a good keyword / Combo with the .com Available I'll Definitely go under this Range .
These results are and can be altered !!! - So don't assume the results are correct ~ Ovt can mess you up on the Plural / Singular thing as well. Which one would you type in yourself ? Apple or Apples ?
If You are talking about Development of the Domain ~ You are chosing the Category yourself - So chose wisely !
Good Luck ~