It depends. Both indoor and outdoor small cells will earn you Helium MOBILE tokens following HIP-51 and HIP-53. Your decision comes down to where you want to install the devices and the coverage you want for your setup.
The MosoLabs indoor small cell is simpler to install and is perfect for covering indoor spaces. A small cell that is mounted indoors can provide limited outdoor coverage similar to a high-power WiFi access point.
The MosoLabs outdoor small cell requires a bit more effort to install and must be mounted outside per federal regulations.
Both indoor and outdoor small cells will need a GPS signal to operate – outdoor needs a clear view of the sky while the indoor uses an external GPS antenna that must be mounted on or adjacent to a window.
The MosoLabs indoor small cell is a category A device and the MosoLabs outdoor small cell is category B device according to federal regulations.
The related regulations are part of the Code of Federal Regulations:
47 CFR § 96.43 - Additional requirements for category A CBSDs
(a) Category A CBSDs shall not be deployed or operated outdoors with antennas exceeding 6 meters height above average terrain. CBSDs deployed or operated outdoors with antennas exceeding 6 meters height above average terrain will be classified as, and subject to, the operational requirements of Category B CBSDs.