Today? Yes, Longwell is better (even if he usually kicks in a dome and has far less leg strength). Longwell has been kicking for so long now that it's automatic for him.
HOWEVER.... I'll take Crosby after 4-5 years over Longwell after his first 4-5 years. Longwell also wasn't much of a fan favorite during his first five years here.
Basically, I like Crosby more at this stage of his career then I did Longwell at the same stage. If Crosby continues to develop in his mid-range kicks then the Packers have their kicker for 10-15 years. I'm not a fan of 50+ yard field goals (too much risk and not enough reward unless it's end-of-half kicks) but I do think his leg strength will be valuable for kickoffs now that they're moved up to the 35-yard-line.
Now if Slocum still has Crosby doing those pooch kicks then I will be very disappointed.
Unless we could replace Crosby with Adam V or Rob B, I wouldn't even consider being one of those teams that change their kicker every 8-16 games. There's no kicker that's going to give us more than Crosby and there certainly isn't a free-agent kicker with his potential.
All I'm saying on this