Separate tracks per person
The single most useful feature. Separate tracks let an editor level each voice and remove one person's cough without touching the others. If a tool only saves a mixed file, editing is harder.
Local recording
Some tools record each speaker's audio on their own computer and upload it later, which avoids internet dropouts. Others record the call itself, so any connection problem is in the file. Local recording usually gives better audio.
File format and quality
Look for uncompressed or high-bitrate files, such as WAV. Compressed files lose detail that an editor cannot recover. Check the sample rate and whether the tool changes it.
Reliability
Does it save while it records? Does it recover after a crash? Test with a short call and a deliberate disconnect before a real interview.
What you do not need
Features such as built-in editing, live streaming and large guest lists are optional. If you plan to hand editing to a producer, choose the tool that gives the cleanest raw files.