Benchmark: DOTA 2, Rainbow Six Siege, World of Tanks
For representing the multiplayer online battle arena type games I've used Dota 2 as its replay system is excellent for accurate benchmark results. I'm able to repeatedly target a busy part of the game to test. I'm not bothering with League of Legends as it's less demanding than Dota 2 so if these cards can play Dota 2 you can rest assured they can play League.
Using the lowest quality preset which is called "fastest", the GT 1030 rendered just 4% more frames on average but did allow for 20% greater 1% low result. Much the same was seen when using the best looking preset, here the GT 1030 was 23% faster than the RX 550 for the 1% low result despite both delivering the same 60ish fps on average.
If you plan to play a lot of Tom Clancy's Rainbow Six Siege then the GT 1030 looks to be the best option here. Using the low quality preset it was 9% faster than the RX 550 but again it's the minimum frame rate that makes the biggest difference and here the GeForce GPU was 31% faster.
It's a similar story using the high quality preset though both the RX 550 and GT 1030 did deliver a similar average frame rate. The overall experience however was better on the GeForce GPU as it maintained a 17% better 1% low result.
World of Tanks was tested using the HD client with the frame cap removed. Using the low quality preset which is titled "minimum" we see that both GPUs allow for almost 200fps on average and the experience was much the same using either the AMD or Nvidia hardware.
Jumping from the minimum quality preset to high saw a massive decline in frame rate and this isn't even the highest quality preset in the game, neither GPU delivered what I call playable performance using the maximum quality preset.
Anyway using high the GT 1030 was 17% faster than the RX 550 on average and a massive 35% faster for the 1% low result.