Can't comment on either. But the one for 20 bucks is worth a try. If it doesn't meet your needs the cost is not a killer.
I paid $100.00 for a Gast with filters, valves, etc. Got a real bargain.
Understand, if you are stabilizing, the solvents (Acetone, MEC, etc.) will eventually destroy any plastic parts inside. I know I'll have to do a rebuild on my pump eventually.
BTW, for stabilizing, I am not a believer in using pressure. A well known law of physics is that nature abhors a vacuum. If you only use vacuum the solution will fill the voids.
You got me to thinking (that doesn't happen often ) the $20.00 pump might be worth me trying. At that price, it will be cheaper for me to discard and buy another instead of rebuilding my Gast.
The IAP penturning forum has an active area just for casting and stabilizing. You might want to check it out.
Good luck. Let us know what you do.
"Folks is funny critters."
Think for yourselves and let others enjoy the privilege to do so, too. ~Voltaire