3 gallon V 5 gallon

depends on how big you grow your plants and if you are going to change vege length / plant sizes etc.. in soilless and a typical ~4 month growing cycle, it's not going to make much of a difference. in soil, you might see slightly smaller plants result. plant size can be restricted by pot size, but your methods of fertilization will make a difference. in soilless, a plant is fed more efficiently and that mitigates pot size changes more than soil. have you ever looked at the resulting root mass after your grows? is it heavily colonized or is there a lot of volume of soil with little to now roots? This can help you choose if you can down-size the pot. If it is over-crowded and approaching rootbound concern, then you know to stick with the 5 gallons size. again, soilless/hydro will be more tolerant to these conditions, too. autos have a short vege phase, so a 3 gallon pot is plenty large enough. If you grow a photoperiod with similar vege phase length, you'll want a similarly sized pot. auto vs photo is not relevant beyond that. simply about how long a plant will be in that pot. so take a peak at your roots... if they have plenty of excess space and not crowded, you can downsize without any issues in a confident way.

Picking pot size is really about determining the best volume that pairs best with your chosen substrate, its consistency, and the frequency you wish to irrigate. The oversimplified bigger pots = bigger roots = bigger plants philosophy applies moreso for your soil grows, especially if you're trying to go it alone on a living soil without later amending. Some of the biggest plants I've ever seen were grown in 1 gallon, hydrate and go type coco blocks that just got short irrigations like 3x a day. If you're not running an automated system though that's a lotta hassle. Bigger pots need to be watered less often, even moreso with soil. Adding other materials like perlite help with managing moisture too. This applies to both autos and photos really. What your pot is made from matters too. Fabric is best in my opinion. Plastic is ok, airpots being better. If you have terracotta, smash it with a hammer and get one of the previous lol.

I run 3 gallon for photoperiods, 5 gallon yields were the same. I grow in a tent so the plants can only grow so tall before needing to flip. If height wasn't an issue, I see 5 gallon be more beneficial. I would say go with a minimum of 5 gallon for Autos, I had issue with 3 gallons and root space with Autos and is why I say go with a minimum of 5 gallons. Another reason I like 3 gallons for photoperiods is because it uses less medium. I run 6 plants in 3 gallon in my 8x4 photoperiod tent, that's 18 gallons of medium. 3 plants in Auto tent in 5 gallon is 15 gallons of medium, only use 3 more gallons in my photoperiod tent growing twice the plants in 3 gallon pots.

Have done both, been setting on 5 gallon (20L) since I felt the plant cannot expand fully in 3Gallon (11L), I did have way more harvest under same lights with Autos, No difference in Photos even with longer training (at least for my one run I did with photos to compare). Since I do mostly Autos I will only go 5Gallon and already threw the 3Gallon ones out...

I haven’t done photos in three gallon pots to be able to tell the difference between yield in photos and autos. But I do autos in 3 gallon pots and photos in 5 gallon pots. My purple punch auto yielded 67 grams. My critical cheese auto got 106 grams. My photos yield 120-150 grams in 5 gallon pots. Yes pot size matters when it comes to yield but so many other factors come into play with yield and overall quality. I’ve also seen growers get massive yields in 1 gallon pots. So grower skill levels are the biggest factor really.

5 gallons is close to 2x the amount of real estate for roots so i would say if your growing large plants yes the extra room will for roots will help make larger ppqnts