All discones perform more or less the same, if they have 8 legs or more and they are at least 25" long. The difference are the build quality, how well they stand up for wind and rain/snow. Placed indoor in the attic it doesn't matter but outdoors you can either get a cheap one and replace it more often or change to another antenna type if you where not satisfied with it, if it's easy to do, or get a more expensive one that will last longer if it's difficult to reach to and work with. To receive well at low-vhf you'll need a discone with a top whip but that will have a narrow frequency range.
/Ubbe