Well, I was a HD GS user. Then I tried a Proline GS.
Pros: Rinses Well, Almost to new; Very soft, can bend and shape into nooks and crannies that the HD GS cannot go.
Cons: Doesn't hold water was well as the HD GS. Also, doesn't seem to pull dirt away from the paint as well as the HD GS. I had to go over some spots a few more times than the HD GS.
Bottom line: The Pros are created b/c the very-porous nature of the Proline. However, this also creates the cons, the extra-large pores also make it more more permeable with water. Water 'flows' through it well (makes a better rinse), but also disables its ability to hold a lot of water. I also thought the pores were too large and didn't capture all the dirt. Thus, I had to go over sections more than the HD GS.
Which to use: I've come to realize, I'm dropping the GS concept overall. Too many trade-offs with both. I've been using the Walmart WW now. They are super soft: When folded, gives me 16 sections per towel to wash. I use 6 towels to ONR wash my car. (4 wash: 2 Dry) No need to rinse the towels just use then get a new one. I only use 1 Gallon to wash the car. At $3.00 for 2, it's a steal. GS (HD and Proline) will get relegated to the wheels.
These are only my expressed opinions. Use what works well for YOU. Please ingest my commentary like a tomato: With a grain of salt.