There are similarity between GT 1030 and RX 550, they were released in the same year precisely in 2017.
Both of video card, among choices in this class are the best and also the most interesting option to have for a budget gamer.
GT 1030
As part of GeForce 10 generation, this gen is full of exiting product from GTX 1050, and GTX 1060 and also Titan X Pascal.
That said this GT 1030 is the weakest from its generation, since it's just an entry level and is made for budget gamers as a Best Graphics Card Under 100 Dollars.
But if you want to compare it with older video card that were intended as mid range product such as GTX 650, Radeon HD 7750 or HD 6670, then you can see the specification and performance from GT 1030 is better.
With this card you can run Need For Speed Heat and gain around 30 fps in 720p low. The similar result can be seen with Jedi Fallen Order games, but you can enjoy better visual in medium settings.
The result is better for older games such as Rise of the Tomb Raider that was released in 2016, where it can max out the games setting in 768p resolution and the frame rate above 30 fps.
Probably the most interesting point about the video playlist above is the GT 1030 can run well with old dual core I3 3220 processor, and no bottleneck are found. Therefore, GT 1030 is a perfect combination to pair with old generation CPU if you want to build a low end gaming computer.
RX 550
The good thing about RX 550 is, even though it's just an entry level card, the performance can match the mid end video card from previous generation such as GTX 650 Ti and HD 7790.
One of the biggest difference this RX 550 with GT 1030 is, it's available with 4Gb DDR5. While GT 1030 is available with just 2Gb DDR4 and DDR5.
Bigger memory size means you can run games that require 4Gb Vram like latest series of Assassin's Creed and Resident Evil Village better.
According to video above, there is a different of performance between RX 550 2Gb and 4Gb in the games tested, with the 4Gb version can show better performance in this test.
see also: GT 730 vs GT 1030: ideal Graphics Card choice for 720p
Which one is better and stronger?
GT 1030 has stronger base clock, but RX 550 has faster memory clock and bandwidth. On the paper RX 550 will perform slightly better than GT 1030, plus the difference between those product according Techpowerup can reach 21%.
And if you see the video test on YouTube, you can see that RX 550 can beat GT 1030 in those test.
Conclusion
If you want better performance then RX 550 is your right choice. But GT 1030 also looks attractive with the cheaper price and also it's lower power consumption.
If you want to get RX 550 make sure you get the 4Gb memory size variant instead of 2Gb.
And for GT 1030 choose the DDR5 variant instead of DDR4, since the price is relative same yet the performance is like night and day.