Unfortunately I find Pilot G2 to have loose tolerances between the refill tip and pen body. It's like 1.5-2 thousandths of an inch, compared to 0.5-1 thousandth for Uniball and Pentel bodies. It makes your writing a bit sloppier and more effortful.
I believe the Uni-ball One is a better pen body in every way. Tight tolerances. Well-built, hinged steel clip that provides superior fidgeting. Nicer clicker haptics too. I don't love the ink that comes in them, but they take Jetstream SXR-7 and SXR-5 refills. You can get both of these from JetPens.
I used to use Pilot G2s and was a huge advocate for them until I tried the Uniball Jetstream RT. I just think it writes more smoothly.
But I've never actually had to put a refill in -- I bought a 3 pack of those about 8 years ago and they're still all going strong. I just don't write enough.
The G2 05 used to be my pen of choice but within the last few years I've noticed the ink tubes dry out and become unusable long before they actually run out of ink.
I'm also a decade long user of this pen right here.
In the 1980's I preferred Uniball pens. Back then they had unreasonably high construction quality for a disposable pen with precision fitting parts and a stainless steel clip. The roller and ink were also very high end for a disposable of the time. Unfortunately it doesn't look like they build them like that anymore.