Phillip Welds(not sure if that’s right) vs vertical welds strength.

First I want to say I'm not a welder, I just have a question about welding.

My dad has been making me watch this YouTuber so I can be more independent and in this particular video the gentleman was talking about securing a load to a trailer, particularly an little excavator. He mentioned that it was better to secure your chain hooks to the D-Rings because they're stronger than this square bracket thing on the side of the trailer (that looked like you could fit an upright board into.

Here's the part I'm confused about and just want to learn, he said the D-ring is stronger because its welded with a Phillip weld (maybe Fillup?), vs the square bracket thing being welded differently, and he pointed to the square bracket being an up and down weld rather than a weld that goes parallel with the ground. I'm so confused why this would be stronger, and admittedly I know next to nothing about welding, but can some one explain this to me?

Also if anyone wants to find the video it was by Essential Craftsmen.