Yeah, but if you run both Collector AND Dual Ball, you could easily get a full bench T1 and not need to worry too much about not getting things set up. That's why I think it's a good idea to run both.
Let's say you have an opener with a Collector, 1 Dual Ball, 2 {L} Energy, Junk Arm, Thundurus, and a PONT. This is a pretty good start and it doesn't always happen, but let's just do this for the sake of argument. You play your Thundurus as your Active, attach, try Dual Ball. Okay, 1 heads, not bad; get a Tynamo. You opt to be adventurous and Junk Arm (to discard the other Energy and Collector) and Dual Ball again. You get 1, maybe 2 heads this time. Get another Tynamo and either a Zekrom or a 3rd Tynamo (or even Cleffa). Now your hand has only one card, the PONT. Use it. Oooh, we've got Skyarrow, Level Ball or 2, another Energy...some more goodies! Then you can Charge your Thundurus and you're good to go.
Cutting to the point: there is nothing wrong with running both, and that can help you get a strong early-game presence as well as maintain a good late-game presence; running enough Dual Ball means you're running no more than 2 Collector and you don't run the risk of drawing them late-game (which you NEVER want to do). Most people, on average, get about 1.4 Heads with this card I've noticed - most of the time they get 1, sometimes they get 2, and once every so often they get 0. But it doesn't waste your Supporter for the turn so you're free to use Oak or N or what have you. With Collector, you aren't able to Oak that turn and see what else you get
I'm not saying that my approach is the right (or the best) one, nor am I saying yours is wrong, but I've noticed that builds that use Dual Ball are generally better off, and they tend to have a stronger field presence. (As a rule of thumb, I tend to run 2 Collector and 3 Dual Ball in my decks, except when I use Vileplume, in which case I run 3 Collector and 0 Dual Ball instead.)