Outer Limits 4x4 Board

Evening All;
I have a 79 series Cruiser Ute with the Turbo Diesel motor (1HD-FTE).
I am going to upgrade the exhaust to a 3-inch mandrel bend.
Two of the shops can supply with a 3½-inch dump pipe and the others only have a 3-inch dump pipe.
However, the 3½ costs about 2-300 bucks more.
Anyone had any experience with the bigger dump pipe?
Common sense says its better, but that much better?
Anyway, give me your ideas.
Thanks
Pony

If the rest of the system is 3", is there any point going 3.5" dump pipe?
There will be a bottleneck when it restricts back to 3"...