Wow. Lots of misinformation in here about Petrus, at least from what I know. For reference, I quit cubing for about a year around this time last year, and at the time was around 9.5 for my global average, and I used Petrus. Petrus isn't fast. But neither are CFOP, Roux, ZZ, etc. The reason being is a method can't inherently be fast because its just a way to go about solving the cube. People can solve the cube fast using methods, some being more popular than others which gives a false sense of "No one uses this so it must be bad" or "Everyone uses it so it must be good." Every method has their flaws but many have benefits to make up for those flaws. For example, CFOP is very set in the manner of which you do the steps. Your cross solutions most likely all look similar, F2L solutions, etc. This simplicity allows for fast TPS and easy look-ahead, at the cost of being restricted to essentially RULF and a few rotations. Roux has its benefit in its linearity. You will always do LB/RB/CMLL/EOLR/4c. But because the first step is always RB, you can choose the most efficient RB you find, which allows for better lookahead into SB, and so on. The downside of this is a large portion of it is intuitive which many seem to struggle with, but has the benefit of lower movecount meaning you don't need to worry about TPS as much. Petrus on the other hand, hasn't been explored much, if at all. We all know it ends with the EO:LL state, where ZBLL can be used to solve it. But so can Fish and Chips, OCLL/PLL, COLL/EPLL and so on. But that's one of Petrus' downsides. It is linear and largely intuitive (excluding EO, which imo should be algorithmic similar to CFOP's F2L where you learn it intuitively but drill it to essentially algs) which creates a large area where there isn't much that can be adjusted. Take Roux for example. In its infancy, Roux's last step, which is LSE, was very uniform of EO/LR Edges/4c, but as time went on it was essentially altered to be EOLR which is the first two steps combined in to one step. This isn't doable in Petrus unless you are crazy at blockbuilding and can direct build a 3x2x2 (No expansion whatsoever) Similarly, many people do/did EO with Petrus "wrong." In this case, wrong doesn't actually mean wrong, but rather sub-optimal. People will build the block on the left because that's how many tutorials taught it and do EO RUFBS, when actually it is better to do it with the block built in BD, so that your EO is now RULFM which is a much better movegroup and also allows better look-ahead from EO into F2L as you rotate back to do F2L 2-gen as you no longer have a blind spot, which is common in other methods unless you specifically avoid it.
As for the misinformation, "...solving a cross edge and then doing EO and then F2L..." -- tx789
This is blatantly incorrect, as you do not solve DF/DR depending on your block location and then do EO. You do EO and then your F2L, and very rarely do I ever do it by placing DR and then 2 pairs as it is less efficient and removes the blind spot benefit I mentioned earlier.
"You solve a 2x2x3 block then EO, then solve F2L. The last two pairs of CFOP is way faster than that. Solving EO isn't even that good. Cubes are much better these days " -tx789
Again, there's a bit incorrect here. The last two pairs of CFOP is not analogous to RB of Petrus. It isn't a comparison that makes sense.
"Solving EO isn't that good" I believe most people would beg to differ. I mean, there is a reason so many people use partial edge control to avoid dot OLL's right? All of the OCLL's excluding H and Pi (I believe) are all able to be oriented in about 7 or 8 moves. Compare that to standard OLL's average movecount. Again, if you have a lower movecount, you don't need to turn as fast which is where Petrus' strengths lie.
"Cubes are much better these days"
While not incorrect, it is irrelevant. I can pull out my old dayan Lunhui and get the same times on it as I do my GTS3/Tengyun/Whatever else.
"Roux has fewer average moves and requires far less algs. There are also less long pauses due to Petrus requiring early edge orientation." -- Izaden
You mentioned you were very new, but that doesn't mean that you can pass false information off as fact. Nothing against you here, you're new, but Petrus and Roux have very comparable movecounts, and I believe using HARCS they both average around 40 moves, though Roux may be a move or two less, but that's a computer. Someone who has essentially mastered Roux and another who has done the same for Petrus should have virtually equivalent movecounts.
"EO has almost zero benefits..." -- u Cube
EO has nowhere near zero benefits. Lower movecount, easier look-ahead, better movegroup, the list goes on.
"Petrus is better on old hardware like 2003 hardware. EO first is better, but is EO that useful for solves. RUL is a bad move set RUD is much better." --tx789
Hardware is irrelevant as everyone is on the same hardware now, and everyone was on the same hardware in 2003. I'll ignore your EO statement to avoid repeating myself more. As for your statements on movegroups, RUL isn't bad, and I agree that RUD is better, but neither are used in Petrus except for in LL and on occasion F2L -- special cases and keyhole respectively.
TL;DR: Seems a lot of people don't know methods as well as they think they do, and attempt to pass off said misinformation as fact. I call them out on it