Where are you getting ads?
I don't know if the G2 has 4.4.4 but my GS5 does.
What i found is that there is always a trade off. If you want marginally faster performance, you use the ROM. But for months there was the Lock screen of death issue. The "knock-on/off" feature didn't work, camera issues...
When basic functions of the phone don't work, or need clunky workarounds that "sorta" work, it simply isn't worth the 5% perceived performance improvement.
And the reality is that you don't know how much faster it is than stock, unless you disabled all the bloat(which is easy) and tried alternate launchers with the animations turned off, transitions set to the minimum, etc...
Most of the real world performance improvements with a custom ROM, stem from the launcher that the ROM comes with.
And a lot of it comes from placebo, or from simply doing a clean install. Windows(any version) is always faster when you do a clean install, but after 6 months you notice it slowing down. With ROM's, you are updating, what once a week? Nightlies? Most people clear cache and dalvik when they install a ROM or even a nightly, just to make sure that it is "clean"...
That alone, will make the phone seem faster. Take your stock phone and do a factory reset 3 times a week, and I guarantee you will see a performance improvement. LOL