Halberds don't affect initiative, so I guess it's whether you want to do damage or survive.
WS4 doesn't just affect what you hit on, it also determines how easy it is for the enemy to hit you. Being hit on 4s is much more preferable to being hit on 3s. Swordmen will also get the 6+ Ward save from the Hand weapon and shield that Halberdiers won't.
On the other hand, Halberdiers wound T4 on 4s, rather than 5s, and T3 on 3s, rather than 4s, which is a major improvement.
WS4 doesn't just affect what you hit on, it also determines how easy it is for the enemy to hit you. Being hit on 4s is much more preferable to being hit on 3s. Swordmen will also get the 6+ Ward save from the Hand weapon and shield that Halberdiers won't.
On the other hand, Halberdiers wound T4 on 4s, rather than 5s, and T3 on 3s, rather than 4s, which is a major improvement.