Arena team mods...

First slice lower ones to gold. You may get several speed increases.

In arena, speed is king. Slicing to 6E won't increase speed on any of your mods except arrows with speed primary, which will go up to 32 speed. A guaranteed +2 speed is no bad thing, but you have a 25% chance of rolling 3-6 speed each time you slice an E/D/C/B mod with a speed secondary. It's higher risk, higher reward and requires fewer resources.

That said, I've sliced 5 times so far and haven't rolled speed at all :(