I am by no means an expert here, but I will give my honest opinion.
I just recently bought a Grizzly Jointer go550x (helical head) or spiral as they call it. Very nice machine.. no major complaints.
I then ordered a PowerMatic 15hh planer. (Helical Head)... Great machine.
All I can say is that in my opinion the fit and finish on the powermatic is better. I have no major complaint with the grizz as is does what it is supposed to do and I feel it will last many years.
The Powermatic just seems to be a grade above. Heavier castings and better qual on the paint job. Mirror finish on the tables. I am very pleased with it.
Oh, buy the way I looked at the Jet version of the same planer after I got the powermatic... I would buy the grizz before the Jet.
Just my opinion... hope not to offend anyone.
I think you meant the Grizzly is a planer... at least the G0550 is a planer, it is an older motor on top 15" 4 post planer to be exact.
There is considerable fit and finish differences between the current G0453 planers and the PM15 planers, The Grizzly is from China and the PM is from Taiwan. The Grizzly castings are much rougher but it is impossible to know (whithout some severe disassembly and testing) to determine of the insides are as different as the outsides. The PM does have a warranty that is 5 times longer, if that means anything to anyone and if you get one of the last few Onyx 90th anniversary PMs around they have an 2.5 years of warranty and are priced the same as the mustard versions. Occasionally you will see people opine that all the generic 4 post planers come from the same factory, difficult when they are built in different countrys. The value is with the Grizzly, certainly. The other big difference is the journal head, the Grizzly uses a generic Asian straight cut head where the 15HH uses a US made Byrd that has uses radiased carbide bits set to shear cut, FWW tests came to the conclusion they produce a better surface finish. The bits for the Byrd heads about $3 each vs $5.20 for the Grizzly bits, so each full cutter change will save over $150 with the PM but it will take a LONG time (longer than you will get with hobby use in a lifetime) to recoup the difference. The PM15HH would be my choice when it is on 15% off (happens 2-3 times a year) when it isn't on sale it becomes a much harder proposition but with the PM you are giving a sizeable portion of the total sale to a US manufacturer in Byrd.
Now the OP is talking about the 20" versions and I am assuming they are comparing the G0454Z to the 209. My same opinions of the differences apply BUT the price differential is $1500 shipped and the full retooling cost difference is about $220. Again onsale when the difference is closer to $800 I would get the PM, for $1500 I would say get the Grizzly.
In the end I wouldn't buy either, even at dealer pricing you can get a solid PM180 with a Byrd head installed for less than the cost of the non-sale PM. that 18" planer weighs about 50% more than those 20" planers. Though the old PM planers are well regarded they still aren't the top of the heep, but for $4k you can easily get a very nice Oliver 399, probably even with a grinder/jointer attachment. Once you get the hang of using a grinder and get over the fear of using the jointer it will become clear it is easy to get a better finish with straight knives on this level of planer than with a Byrd head and certainly the straight Asian carbide bit heads.