The rate column already is adjusted for time...it's grams per second. The 416 is better than the 413 by a small margin, but less than the corded on 20v. It sits in the middle of those two. What isn't factored in though is price...the 413 is cheaper than the 416. The 414/418 are only a smidge more than the 416 (at least here in Canada today, regular prices, the 418 is only $30 more than the 416 both as bare tools). This plays into the argument that there's no point in doing a 416 when for a few bucks more, you get a WAY better grinder and you still need to go buy 60v batteries either way.
Your rate shows material removed given the time ran however it's simpler (IMO) to simply look at model "z" removed "x" amount of material versus model "y" using equal time. Now you can either increase the time of the one that ran shorter time or decrease the time of the one that ran longer either way you see the actual material removed if time is equal.
Using exact time for comparing models the 416 significantly outperforms the 413. 4.0 material removed vs. 3.2 on the 413.
With adjusted time the 416 is within a margin of human error to the corded model.
3.92 material removed versus 4.1 that .2 difference has to be close enough to fall in the human element.
Cost....
Let's use Home Depot on all...(different places have sales but just use one vendor)
They are all within the same ballpark.
Price difference is negligible.
The "need" and battery availability is the driving force here.
If you NEED a big powerful grinder then you have to get a 60v.
That said once you committed to the 60v it's the only battery you can use. You can't use any 20v on it and grinders are battery hogs. You'll need more than one 60v for and possibly more than two.
In my case I was grinding/cutting for 2 plus hours straight. I had 3 60v at the time and I out ran my batteries so I had downtime. (Can't use a 20v on a 60v tool) even with a fast charger
Yet I had 8 20v batteries ready to go staring at me that couldnt be used.
Hence why I got the 416. I can use the 60v on both the 413 and 416 but if I get a bump in power for a negligible price difference between those pair I'm going for it.
The other factor is size. Using them with plenty of room the 60v wins. If you're working in tight spaces the 60v grinders are bigger and can mean fit vs. no fit for the task at hand.
As I said before the 60v grinder is impressive. More power than any Milwaukee I've used.
But the 416 definitely has a place in the lineup.
If someone already has a mix if 20 and 60v batteries the 416 is a great option.
I wouldn't buy it aiming to get the boost I need with a 60v battery. If anyone is doing major work you need batteries. Lots of them and the 60's are damn expensive stand alone. But if you've already got a mix of batteries and just happen to need a grinder the two logical candidates are the 416 and the 418
