With a Pi3 you get more USB ports (diversity, serial ports via FTDI etc.) and more compute power (more config options - FEC rate, less latency - ARMv7 instructions for packet encoding/decoding in the future). Only use the Pi Zero if you do not have enough space or money.
Pi Zero W
Other untestet hardware that should work just fine
NVIDIA Jetson (Nano) (works with RPi Camera v2 out of the box) (*)
A wide angle lens is recommended. There are some V1 models with that.
Pi camera module V1
Pi camera module V2+
Any other camera supported by linux should work as well. However you need to change the start scripts manually to feed the video to the video air module stdin. The latency might be higher than with Pi camera modules.
Following chipsets work:
Ralink RT2070, RT2770, RT2870, RT3070, RT3071, RT3072, RT3370, RT3572, RT5370, RT5372, RT3573, RT5572
Experimental support added in v0.6
Realtek 8812au (RTL8812au)
CSL 300Mbit Stick (2.4/5Ghz, Diversity, RT5572 chipset)
Alfa AWUS036NHA (2.3/2.4Ghz, high power, Atheros AR9271 chipset)
Ubiquiti Wifistation USB (2.3/2.4Ghz, high power, Atheros AR9271 chipset)
TPLink TL-WN722N V1 (2.3/2.4Ghz, Atheros AR9271 chipset)
ALFA AWUS051NH v2 (2.4Ghz/5Ghz, high power, Ralink RT3572 chipset)
ALFA AWUS052NH v2 (2.4Ghz/5Ghz, Diversity, high power, Ralink chipset)
TP-Link-TL-WDN3200 (2.4/5Ghz, Diversity, RT5572 chipset)
Rosewill RNX-N600UBE (2.4/5Ghz, Diversity, RT5572 chipset, txpower unknown currently, RT5572 chipset)
AW-NU138 (2.3/2.4Ghz, Atheros AR9271 chipset)
It is recommended to try and match chipsets on the UAV & GND station.
A single high power card may be on the UAS. On the ground you can decide for yourself. A high power card is not required since the set data rate is much lower. More than one card/antenna is recommended on the ground station.
For 2.3/2.4/2.6 GHz
TP-Link TL-WN722N V1.x
Ubiquiti Wifistation (EXT)
For dual band (2.4/5 GHz)
other cards with external antenna and RTL8812au chipset.
For higher output power & range a high quality low noise amplifier (LNA) may be added to the antenna output of the cards. This may or may not improve the systems performance. Make sure you stay within the local regulations (EIRP).
TX-Power as reported by some users & the internet.
IMPORTANT: Make sure that you stay within the local EIRP limit. In many countries an EIRP > 100mW is illegal! A range of 500m-1000m might not look like much at first glance, but it is enough to get 99% of all shots you might want to take when using DroneBridge for aerial photography and many other applications.
Some users demonstrated that ranges of 10km or even 34km are possible. However, because of legal concerns and safety precautions it is not recommended to push that far.
befinitiv - wifibroadcast
Rodizio1 - EZ-Wifibroadcast project
seeul8er - DroneBridge
People of the internet and the rc-groups forum