For me, the very best to use in the field, and logging most information will probably be the observation app (obsmapp or iObs:
https://apps.apple.com/be/app/iobs/id713587892?l=eng ), but I can't compare with igoterra and inaturalist as I haven't tried those (is anyone volunteering to try / compare all of those and publish an article

?.
Obsmapp / iObs have a build-in obsidentify function: you take a picture of an insect or plant (or even a digiscoped bird) and the app will try to recognize it. It works very well for some groups (like beetles, butterflies,...) but not all.
Note that ebird only does birds. Other sites do all groups of animals.
The reason I still believe ebird is not great, is their use of hotspots. Hotspots make it easier to get a general grip on an area because it has great filters.
But their use of hotspots are my main gripe: hotspots produce a nice list but it's actually very vague information, and while ebird enables you to use personal markers, it's not encouraged / designed to do this and not many users make good use of personal markers. They keep using checklists and the exact location of certain birds ends up being lumped in the hotspot coordinate, that is often totally unrelated to the habitat of the bird.
Fact is that hotspots dilute location data in a way that they are annoyingly confusing when you are trying to locate a certain species or sighting. The hotspot can be miles off the real location of a certain sighting.
Other sites log sightings while your GPS on your mobile phone is active, so you have exact coordinates for each sighting. This makes it way, way easier to locate sightings of other birders (like for a twitch or travel), and it makes it also easier for yourself to retrieve that info (e.g. when you want to check certain nest holes in the forest or certain fields for butterflies).
Anytime a good bird comes out in the USA, I see all kinds of people giving long descriptions of where to find a bird, often referring to google maps because the link to an ebird hotspot is often worthless. With observation, all you need to do is go to the insert-your-country subsite of observation and all info, with exact location, time stamp etcetera, is there. The only thing needed is a broader userbase ;-)