Double is more forgiving then a single and will have it's place in different hunting situations.
Singles are harder, but there are many different types. Some easier then others.
Comp calls require more skills then, say, a cut down.
How a single reed is tuned also plays a part. Longer reeds, the deeper the tone and easier to use vs a shorter higher pitched calls.
Back pressure is another thing to think about when it comes to control and sound.
Same with forward pressure. Duck calls are musical instruments.
You don't have spend hundreds to get an exceptional all.
IMO, nothing is better than having someone with calling skills to help. Videos are great but a mentor is better.
One last thing, buy local. Find a TX call maker and go see them. (There are plenty) They can assess your skills and match a call to your needs and give you some tips.
If you do get a DR-85, don't get the clear one. They can get gross looking.