The Jackaroo is MUCH larger, heavier, and bulkier. This is partially to allow for the larger 21700 cell. I suspect that the housing and silicon are a bit thicker, too. The Solo, therefore, is lighter and somewhat more comfortable to hold. If you're going to be using wattage around 45 watts (as I do with a single coil RTA), there's not a truly remarkable difference in battery life between the two. I'm running 3000 mAh 18650 in the Solo and 3500 mAh 21700 in the Jackaroo. If you're wanting higher wattage, the better bet is the Jackaroo.