Speeds using a transaction vrs not

I wrote a .net program to move my data to postgres (works great on
SQ_ASCII).

In fiddling around I tried it using the odbc driver and a transaction
originally, but converted it to using the .net connectivity but no
transaction.

What I found was it moved my database (4 gig in MSSQL) in 2 hours using the
.net, but 12 hours with the odbc and transaction.

Have any of you played around to see if using a transaction should be that
much slower or is it the odbc versus .net?

I paid a consultant to look at what would work best and his speed tests
indicated the odbc and the .net were pretty close, so I am assuming it is
because I am using a transaction on my odbc test.
I can run again without it or with it on .net driver, but thought I would
ask.
We only use transaction on important multiple table updates in our system
now, so should not be a huge thing, but was curious.

Joel Fradkin