As @weakfl stated, the Ember chipsets are best (IMHO), and the have the best support (both by the binding and their manufacturers). The EM35x mentioned by @weakfl is a good option, but there aren’t too many sticks readily available. There is the MeshConnect EM35x series from CEL that are generally easily available, but they have no firmware in them when purchased. There is also the HUSBZB-1 from GoControl (a combined ZigBee/ZWave stick available in the USA) that is also ok, but this has quite an old firmware and no bootloader. There is also a Bitron stick sold by Deutsche Telekom, but this requires custom drivers so is only usable on Linux…
Nearly all of the commercial users of the Z-Smart Systems libraries that perform all the low level ZigBee work are using Ember chipsets of various types, so it gets the most testing, and best support.
I would have no real hesitation recommending any of these if you can live with the relevant constraint. Plus or minus, they all work the same with the “same” firmware. However, this is an old product now, and I don’t think Silabs are still making them. Instead, they have a new range - the MightyGecko, or EFR32 range (same thing - different names). Again, this uses the “same” firmware as the EM35x series, so will work exactly the same with the binding.
I am looking at producing a stick with the EFR32 in it - hopefully at a similar cost to the existing CEL MeshConnect sticks. My goal is to solve a few problems that the existing sticks have - it will have a hardware reset (a potential problem with all current sticks that causes some people issues), and it should also allow me to support the sniffer function at the same time as being used as the coordinator (all current solutions require a second stick to act as a sniffer). It will also come programmed, and will include a bootloader so it can be updated, so it should get around all the issues we currently have with the various Ember sticks mentioned above.
Let’s see how I get on with this - I have some boards arriving in the next few days so there’s still a little work required to get this into a working state .
Just for completeness - other options out there are the TI CC2531 dongles - these are low cost from China, but the firmware is not so good and I’ve been told by TI that it will not be updated. The Telegesis is still on my “recommended” list as it generally works fine, but it’s not going to be updated, and it’s not ZB3.0 compatible (I should also say that the Telegesis is actually the same as the CEL chips except the firmware, and the firmware can be reprogrammed with the standard Ember firmware). The ConBee is also semi popular, but not fully supported by the binding, and the last option is the XBee series which I believe works well, but again this is the same as the Ember chips with different firmware.
Anyway, I hope that rather long answer helps with your short question .