The important thing to remember is that the posts are hollow and on their own will not support either fence or gate. Gate posts need to be more substantial than other posts. If the concrete goes in the hole first concrete can be worked up into the post somewhat but this is not reliable so I would eliminate No1. A pressure treated wood insert (no. 2) works well but there needs to be gravel in the bottom of the hole as drainage to prevent rotting of the wood. I am not familiar with metal inserts but this could be more durable ask to see a demo: the strength needs to come from the insert and the vinyl just like a sleeve over it.

To better understand your question, the builder is offering a steel girder over 2x10 girders,(usually tripled), as an upgrade to support your joists? I would go steel, but if you feel that is too pricy,then ask your builder to look into lvl's. They are laminated plywood structural engineered beams that can span great lengths and come in widths and thicknesses that are calc'd for your porject. Dimensional lumber used for girders has been done for a long time, but are more prone to twisting,warping,cracks,etc.Using steel speaks for itself.

I think it comes down to the design of your fence and gate, but like dkv, I'd go with steel for a heavy gate. For light gates, such as pasture gates, we've use fir posts, but when we installed DS's entry gate we used steel powder-coated posts. The rest of his fencing is fir and electric braid. Our gate also has steel posts, but we had brick columns built around each fence post, with light fixture on top.....a little more dressy than DS's.

I think you will say its awesome.. :-) I have to go down 42" to get below the frost line here in northern illinois.. the concrete would be poured around the sleeve first.. so once that sets up you can drop the post into the sleeve.. really I could fill have the sleeve with gravel after that point.. as the post only goes down that far to deal with the frost line.. so I could drop another 10in of gravel into the sleeve and drop the post on top of that.. there would still be 32" of post in the ground.. also whats the harm it in overflowing? seems to me that would take a lot of water.. it would have to soak down to 42inches of soil then fill all the back up assuming it doesn't just keep soaking down in the soil underneath the gravel.. wouldn't all that water just get soaked up by the concrete anyway or pour in through the gap between the post and the concrete at grade.. and the concrete would hold it against the post while the sleeve allows it to drain and or/dry....with the sleeve going all the way down at least the water would have somewhere easy to drain to and the ribs allow for air/drying.. it's not my idea.. these two companies came up with it.. this is the link to the company that sells this product.. http://www.postshieldusa.com/cs/ or this other one.. http://www.postprotector.com/.. i'm just not planning to buy their sleeves but use the pvc sleeves just laying around lowes instead.. i am looking for better alternatives besides dont use ceder and dont use concrete.. seems to me that if any alternative is going to end up with rot eventually why not just make it easier to repair.. i also like the idea of the copper because I intend to use copper on the post caps.. and if it works and looks cool that would be great.. but if that just marginally improves the longevity of the post but you still end up having it rot out and need to remove the concrete then why not make that part easier.. don't know.. these companies at least have me convinced but like they say a sucker is born every minute.. so maybe im that sucker.. I'm here hoping somebody can save me from a dumb idea but it at least seems logical to me.. the post prevents post to soil and post the cement contact which from what i hear are the two things that kill the post..