Type 3 or 4 Full Sink Line for Ponds

I'm about to purchase a higher density sinking line for probing pond depths of say down to 20 feet.

In addition to a floater, I currently carry full intermediate and Type 2 sinking lines.

Any thoughts as to whether I should go with a Type 3 (~3.25 ips) or a Type 4 (~4.5 ips)?

Thanks