Ego C Twist, a mix of both sizes for the reasons already listed. But I would skip the cartomizers and such and just do a standard resistance 510 Joyetech atomizer and some juice.
I feel like people want to carry 1 thing only and it be a "perfect" vape. But remember when you were smoking analogs? You had to have a pack of cigs and a lighter. I don't find that carrying an ego style device or even my Silver Bullet, with the atomizer and a 10ml bottle of juice to be any more inconvenient than the analog days. With that you don't have to worry about the carto's running out of juice, or a tank type system running out or getting clogged. Plus dripping, for me, provides a better flavor and more vapor!
I feel like people want to carry 1 thing only and it be a "perfect" vape. But remember when you were smoking analogs? You had to have a pack of cigs and a lighter. I don't find that carrying an ego style device or even my Silver Bullet, with the atomizer and a 10ml bottle of juice to be any more inconvenient than the analog days. With that you don't have to worry about the carto's running out of juice, or a tank type system running out or getting clogged. Plus dripping, for me, provides a better flavor and more vapor!