In theory, IEEE 802.15.4 (ZigBee, Thread etc.) can achieve a much larger range than Bluetooth Low Energy (conventional, not coded PHY) due to its usually higher sensitivity (see for example here or here).
I have noticed the same in my own experiments, too, but do you know about a reputable source where the coverage of BLE and IEEE 802.15.4 is compared under realistic conditions?
You can check the following research paper titled-"EMERGING
WIRELESS TECHNOLOGIES IN THE INTERNET OF THINGS: A COMPARATIVE STUDY"
Author:Mahmoud Elkhodr, Seyed Shahrestani and Hon Cheung
They have done a full research comparing iot technologies including BLE and IEEE 802.15.4.
This is the comparative study of Power Consumption, Distance Coverage in Meters, and Data Rate.
Zigbee/802.15.4 may operate in different bands (2.4GHz Worldwide, 868MHz ISM Europe, 915MHz US), and the two lower bands have significantly better long range propagation than 2.4GHz. BLE always uses 2.4GHz.
BLE from Bluetooth 4 has only one coding scheme (GFSK, 1 bit per 1 symbol), while BLE from Bluetooth 5 onwards also support two "long range" codings, using 8 symbols per bit resp. 2 symbols per bit, extending the range by a factor of ~4 and ~2.
802.15.4 uses spreading, trading larger radio channel bandwidth requirements for better noise immunity.
When you use 2.4Ghz for ZigBee and BLE, using the same RF chip (many support both BLE and ZigBee/802.15.4), same RF frontend and antenna, expect very similar range (when using coded BLE 5.x).
These sources are good enough. The reason behind these sources showing less range of BLE than Zigbee is because of the transmission power. the higher the transmission power the greater will be the range. There are a lot of devices which work on 2.4ghz in which your wifi routers are very common and have a big range as well. this causes noise and decreases the range of your device. Now usually wifi routers use channel 1-13. Zigbee uses channel 11-26 and ble uses channel 0-39(Now the problems lies here as well). BLE uses channel 0-36 for data transmission and 37 to 39 to advertise, and not a lot of devices give you all of these channels. HM-10 the easiest available BLE device, has 16 channels which overlaps whith zigbee channels which you can read about in TI cc253x/2540 datasheet,here on page 215. So, if you are using wifi, zigbee and ble in let's say a closed space. Then BLE will have a very short range because of noise and if you try to increase the range by increasing the transmitting power, then it will not remain BLE per se, because if you increase transmission power then you are increasing the power consumption as well, and most ble chips are not meant for that. If you need a big range stick to zigbee or wifi for the time being that's what i will suggest.
First let's clear some things. Did i say transmission power is the only factor? No. Is it a major factor? Yes. Next, sensitivity plays a vital role to receive signal but if you are not able to send signal let's say for more than 5 meters then you cannot expect a higher sensitivity antenna to catch your signals 100 meters away. And if there's a way to do it, please let me know considering it fits inside the BLE chip. To make it more clear read friis transmission equation, i think you will get your answer there.
I hope this answer was helpful to you
