>

All this tells me is that there are likely hundreds of top secret documents floating around in random boxes and filing cabinets. I assume this is rather common. Trumps guilt comes from the fact he hid them, refused to return them, likely and stole them to sell.
Voluntarily returned vs refused to return. 
Do the math. >

Also "Classified" vs. "TS/SCI source documents." >

They were discovered by his own attorney. He was the one that notified The National Archives. They promptly returned them.
It seems like there was nothing particularly sensitive there. 
And I guarantee Biden hasn't seen these documents in ages. They were in a box, in his garage, in his former residence. 
Trump had his sensitive top secret documents in his personal possession. In his safe and scattered around his office.  Was asked for over a year to return them to the federal government. Refused to the point that criminal investigators needed to get involved. 
It's not even close to the same thing.