Boomn I think it is a combo of both. I started off with the Canada Hammer a few years ago. I became proficient with the basics on it but had a hard time getting more notes than just the basics. This summer I went to Sportman's Warehouse and tried ~15 different high end acrylic and wood calls. The RNT dirty bird was easiest for me to blow so I picked one up.
It is a lot better. The big difference I can see is the high end calls are much more sensitive and allow you to make slightly different pitched notes, which improved my technique. I have since gone back to the Hammer and found I can make those notes on it also, but it is much harder.
In the end - I think once you get down the basics on el cheapo you need to move to a higher end call to allow your techinique to improve.
It's like driving a car. Anybody can make a car go fast, but once you have been behind the wheel of a high performance car you experience what a car is really capable off.
Fork over the cash and buy yourself a fancy call to go along with your fancy new gun, you only live once