It all depends on how you want it to look. Personally, I do all my neck decreasing so the decreases flow with the neck shaping. It's just the way I like doing it.
If you would prefer the slants to go away from the neck then you could do it this way:
SSK at end of RS rows; SSP at beg of WS rows
K2tog at beg of RS rows; p2tog at end of WS rows.
It's a personal preference.