Seeing Dominons release a lot of people seen the use of fast movementspeed on the battlefield.
As such a lot of people started using Boots of Mobility or Boots of Swiftness, so I decided to make some calculations on both, to see how they stand relative each other.

I dont draw any conclusions as items in League of Legends are all situational, I merely present some math and which should help you make a better choice for your gameplay.

First thing to know is that there are softcaps to speed in LoL, this is to prevent people reaching silly (unballanced) values.

  • The raw speed between 415 and 490 gets multiplied by 80%.
  • The raw speed over 490 gets multiplied by 50%.

This means that once you start building up movementspeed, each additional effect you gain provides a slightly lower effect than before.


--- 310 base ---
Boots of Swiftness

310 + 90 = 400
400/310= 1,29 = 29% faster than base

-Boots of Mobility
310 + 130 = 415 + (25*0.8=20,0) = 435
435/310 =1,40 = 40% faster than base

-Enhanced Movement 5 Superiority
435/400 =1,0875 = 9% faster than boots of swiftness

--- 325 base ---
-Boots of Swiftness
325 + 90 = 415
415/325 =1,276 = 28% faster than base

-Boots of Mobility
325 + 130 =415 + (40*0.8=32,0) = 447
447/325 =1,37 = 37% faster than base

-Enhanced Movement 5 Superiority
447/412 =1,08 = 8% faster than boots of swiftness


Keep in mind, that boots of mobility only gives you the 9% faster while you are out of combat, once you get hit your speed drops to to movementspeed 2 (+70).

-using 310 base
310+70=380 movementspeed
380/435 =0,87 = 87% relative Enhanced Movement 5
-compared to boots of swiftness
380/400 = 0,95 = 95% relative Enhanced Movement 3

Also, Getting boots of mobility increases your chances of reaching the second softcap at 490 movementspeed, reducing any additional movementspeed bonuses by 50%.




-Optimal use of Boots in Dominion
The Crystal Scar contains Speed Shrines, when stepped on they provide a 30% movementspeed buff. Which is quite a nice bonus. However, knowing about the softcaps to movementspeed, this 30% may actually be lower depending on your movementspeed.

--- 310 Base ---
310*1.30= 403,00
(30% movementspeed buff)

-- Basic Boots --
(310+50) = 360
360*1.3 = 468,0 Raw
415 + (53*0.8=42,4) = 415 + 42.2 = 457,2
-No Speedbuff compared to Buff
'
457.2/360 = 1,27 = 27% (90% of original 30% Speedbuff)



-- Tier 2 Boots --
(310+70) = 380
380*1.3 = 494,0 Raw
415 + (79*0.8=63,2) = 415 + 63.2 = 478,2 Total Movementspeed
-No Speedbuff compared to Buff
478.2/380 =1,258 = 26% (87% of original 30% speedbuff)



-- Boots of Swiftness --
(310+90)*1.3 = 520,0 Raw
415 + (105*0.8=84,0) = 415 + 84 = 499
490 + (9*0.5) = 494.5 Total Movementspeed
-No Speedbuff compared to Buff
494,5/400= 1,236 = 23.6% (78% of original 30% speedbuff)



-- Boots of Mobility --
(310+130)*1.3=572,0 Raw
415 + (157*0.8=125,6) = 415 + 125.6 = 540,6
490 + (50,6*0.5=25,30) = 490 + 25.3 = 515,3 Total Movementspeed
-No Speedbuff compared to Buff
515.3/447 = 1,153 = 15% (50%! of original 30% speedbuff)

In other words, the Dominion speedbuff only increase your movementspeed by 24% if you have Boots of Swiftness, and only 15% if you have Boots of Mobility. We also notice the quite staggering fact that the buff Never gives the full 30% bonus unless you have no boots. Even basic boots brings the bonus above the softcap and as such to 27%.