Your question is probably about as big a question as asking are you a Nintendo, Xbox, or PS4 fan!
Personally I use 3Ds Max as it’s what I truly started modeling on. Others I know have started on and prefer Maya. These are two are both Autodesk software and share some similarities but they do have their own ways of doing some things.
Figher5347 will jump in here shortly and recommend Blender as he’s very proficient with it and has some fantastic tutorials for beginners to get them started!
There are several considerations to make about the software before you start though.
Blender is absolutely free, while Max and Maya are not. You can get a trial but that’s only for 30 days.
I would look at the assets you want to create and see if there is going to be a problem creating them within the software. (ie. Max is good with Apex Destructibles where as Maya is good with Apex Cloth)
I wouldn’t worry about which one is more hard to learn. If you’ve not used a 3D modeling software before it won’t matter that much to you. To me Blender is outrageously hard to navigate, but this is because I’m used to Max and stubborn about my controls!
For simple asset creation there is not a lot of difference in how the objects will be seen or used within your game. They can all accomplish this task! A lot of it will be dependent upon your skill and time you put in to become proficient at making the assets you want to create.
On a side note, if you even see an asset in one of the content examples that is offered on the Marketplace you are more than welcome to use that in any game you create. You would simply need to Migrate it from that project to your own project (documentation here)](A new, community-hosted Unreal Engine Wiki - Announcements and Releases - Unreal Engine Forums).
This will work with all the assets. Some functionality of the assets (ie. the minion guy from StrategyGame) will not function properly simply because they have C++ references that will not transfer. The asset will transfer but the functionality that they do in that game will not.
If you have any questions please ask!