Will the migrated data be larger or smaller in Exchange?
The migrated data will most certainly be larger than the source. The change ranges from 1.5x to 3x This will depend on the types and manner of compression used.
There are 2 types of Compression within Lotus Notes and there are a few other options for attachments and message storage that will make a difference.
to name a few.
The actual numbers vary greatly and the types of data stored within the NSF file. Tests should be performed in the said environment to determine the results.