You should be aware that Better X-Ray doesn’t support mods and that’s why the file is so small.
You’ll probably only notice a difference with an extremely low-end computer because you’ll get no lags. However, it doesn’t really matter because both packs are less than a megabyte in size, so they don’t require much memory anyway. Also, there are differences in the file sizes, because they are about four times smaller in Better X-Ray. For example, both support the latest Minecraft version, but the very old ones are only supported by the Ultimate version. Basically, both texture packs are very similar, but there are still small differences. Overall, the Italian developer has created a great alternative to XRay Ultimate with this project. However, this usually doesn’t happen, because the invisible Minecraft blocks are outlined. Therefore, the danger of accidentally falling into lava is huge if you don’t pay close attention. A big disadvantage is that there’s no way to toggle, so you’ll always have X-Ray vision. As a result, you’ll also be able to get extremely rare items, because you’ll have every ore block unlimitedly in your inventory. It will help you progress faster in Minecraft by mining hundreds of diamonds and other ores in just one hour.
You can make all blocks invisible with the Better X-Ray texture pack.