Don't have any experience with Wassel carbs, I can only confirm what Metalflake and KiwiGF have written. I to installed an Amal ordered directly at Burlen fuels a year ago, and it's still performing faultlessly.
I preferred to buy at Burlen because they get you the latest version, with the stay up float and viton tip needle, as where you buy from a distributor, you risk receiving one that's been on the shelve for a couple of years.
It all depends of course how much you can/want to spend, as a Wassel is about 1/2 the price of an Amal, and I suppose a Wassel will do what it says on the tin, but my opinion is that, as usual, you get what you pay for......