I am using :-

• Dell OptiPlex Quad Core i5-2400 8GB 1000GB WiFi Windows 10 64-Bit Desktop PC Computer
• Silicon Power 2 TB External Portable Hard Drive Rugged Armor A60 Shockproof Water-Resistant 2.5-Inch USB 3.0 , Military Grade MIL-STD-810G & IPX4
• WD My Passport Ultra 1TB USB 3.0 Portable Drive

I do not use WiFI, I use ethernet cable 5e from cabling4less.co.uk just £1.32 for a 1m cable inc VAT and postage!  Excellent service too.

Copying from the Silicon Power A60 to the WD My Passport Ultra.

I rather like the Windows 10 progress window.  It took 10hrs 30mins.

So FAT and exFAT differ in size by 4Gb in 925Gb (0.4%).  exFAT is very slightly bigger.