I would base your purchase on how serious you want to get in to calling ducks. I prefer single Reed calls as they have the widest range. But they are harder to become proficient on because they can be overblown and lock up. A double reed has less range but still gives good sound and it has the advantage of being more beginner friendly as they typically won't lock up even when cold and wet.
Now materials will have an affect on tone and volume. Acrylic calls are typically more expensive. They give crisp, loud calls and work very good for open water and calling ducks at a distance. A lot of high end call manufacturers offer the top end "guts" in poly. Poly is cheaper than acrylic and can make some very fantastic calls. It will not produce as crisp of a note but to 99% of people they won't be able to tell the difference. I also believe poly is a little less durable than acrylic. And last you have wood. Wood needs a little more care taken after and during hunts. Wood swells with moisture and can crack calls but just disassemble and let it properly dry after each hunt and it will last a long time. Wood will absord more sound so it gives a very nice mellow natural sound to calls. I love using my wood calls for close up work and finishing ducks.
That all being said I run RNT calls and they are awesome. If your call gets worn out or out of tune you can send them in and they will replace the Reed's and tune it up and send it back to you for the cost of shipping. RNT, echo, zink, etc. All make amazing calls and you can pick up the high end calls in a poly body to save a good chunk of change and still get a great call.
I like the motto buy once, cry once and I've spent a ton of money on lesser calls that got thrown away. But the most important thing is just learn how and when to call and brand really won't matter. After all, if you on the X you really don't need to do any calling at all.