Best Option For Telemetry Radio

What is considered the best type of telemetry radio to add to a vehicle?

Are the 3DR style SiK still considered the best option? Or are the ESP8266 modules preferred now?

Depends on what you want, but these are great

Yeah I’ve read in some of the documentation that those are considered very nice.

What about for a slightly lower price option? Does the community have a preference for UDP vs SiK?

What is your application? The pixracer comes with a wifi module if you are fine with the limited range

My application is a pretty standard multi rotor. I’d ideally like at least the range of the cheap SiK type radios which is about 500 m they claim.

So I guess my question is whether any of the UDP modules can achieve a 500 m range.

No chance to have WiFi over 500m legally. But you can achieve some km with the RFD900+.

Check the frequencies also. 433MHz for EU and 915MHz US, with certain parameters in term of transmit power and so on.

Given that the ESP8266 is an actual 2.4GHz device it’s likely it will interfere with whatever WiFi action/FPV cam you might want to install on the quad, not to mention with the remote control, if it’s one of those operating in the 2.4GHz spectrum. The 433 or 915 MHz radios on the other hand are well outside the WiFi and RC TX frequency ranges so any chance of interference should be minimum. The 433 at least has AFAIK only 500mW of transmit power on either end so their range is quite limited, especially if used with those awful “stick” antennae that the cheap kits come with. Switching to “mushroom” or “pagoda” antennae only makes losing the signal harder, the range is pretty much the same. So if you plan on staying always in line-of-sight mode then the 433 (or 915 in US) should be more than adequate. The ESP8266 is more of a standalone TCP/UDP bridge which you might want to connect through to other boards on the quad frame to control some attached payload packages (i.e. camera zoom, spotlight, IR illuminator, rocket or paintball launcher etc.) In any case the ESP8266 is not very well suited for more than ~100m of clear line of sight as the signal drops drastically. You might consider a pair NRF2401 transceivers with supped up antennae. These can reach 1km+ and be tuned to stay outside the WiFi and RC TX spectra.

It is not a problem of 2.4GHz frequency, but try to avoid using Wifi protocol in serious applications, as WiFi is designed for extreme data rate, it gives very little consideration to spectrum efficiency or co-existence with other radios.

433 or 915MHz band used to be a clean zone, however as the trend in NB-IoT/LPWAN, when massive number of these 100dB+, 5km+ coverage nodes / basestations deployed the assumption will not be true anymore. The bands will soon become as crowed as 2.4G, or even worse.

Compared to which frequency band to use, coding schemes or some kind of frequency hopping(FHSS) is much more important to achieve the minimum probability of packet loss. Advanced coding schemes usually means higher cost of radio, so at least find a radio with some kind of FHSS implementation can give you much more robust performance.
Unfortunately neither Wifi nor a nordic 2401, as well as a large bundle of RC transmitters in the market, have FHSS feature.