The 899 uses the compact transducer first, second bird uses the side imaging returns to computer generate the down imaging. The Lowrance units use a dedicated DI crystal for down which gives you a much better picture. Now if down is all you want the birds with the down only transducer give a picture that is comparable to the Low. I said all that to say this, if you want DI and SI but DI is your priority then I would go with the Lowrance. And I run a 998 so not biased one way or another.
Proud Member of Team Geezer
Charlie Weaver USN/ENC 1965-1979