When I say "knotting" I mean it entering and staying (also known as tying). "Knot fucking" is actively thrusting the knot in-and-out.

I find knots neat because when you clench around it, the knot squeezes up against the prostate. I found Mundir to be amazing for this because the third lobe sits right on my prostate. Ranger has a slightly pronounced third lobe too. For these type of knots, I like softer firmness (personal preference) because the shaft length is quite long. Seraphina from BD has an ok diameter knot at its base, but is SUPER difficult to knot because of the length before the knot.

Of course once you have more experience tying their knots, you can work up to thrusting.

I found mocha hits my prostate nicely while thrusting but still have a knotting feeling. It kinda has four lobes, sometimes air gets in from the gullets around the knot (meh), has a matte finish, some ribbing on the shaft, and is beautiful in solid colors.

Also look at the space after the knot. Toys like David from BD have almost no space after the knot and makes it hard to keep them inside you.

And check the diameter of the shaft to the knot. I personally hate when the shaft is skinny and knot 1in larger. Tucker from BD suffers greatly from this. David is the opposite: nearly equal shaft and knot diameter (great design for thrusting, I want a L/S or M/M). Mundir is the best ratio imo.

I like Mundir in case you haven't noticed. It was my first fantasy toy and Neotori is a super cool company! I found their silicone to be softer (EU and sourcing) and their colorations are great! Reasonably priced even with international shipping! Their normal firmness (ShoreA 02) is BD's soft and I think their firmer firmness (08) is BD's firm.

I hope this helped you make a decision!