+1 for Willtill's comment above. The HeliBars do tighten up the handlebars and make the bike more comfortable... but they don't address the fork flex as a brace does.
I recently installed HeliBars, and had read (or mis-read) others comments that they didn't feel the need for a fork brace anymore, and so left my SB off. After reconsidering the geometry of the steering stuff, I reinstalled the SB, and I'm glad I did. The brace does still make a difference, imho.
Ride safe!