Well I am not quite sure what you are asking about fundimental differance the PB puts lead against the barrel and is a big soft lead bullet best used at about 12or 13 hundred fps [80 gr] the saboted bullet is completelyenclosed back and sides with only the front open and is a smaller caliber than the boreand is usually a jacketed bullet and is normally shot from 1500 to 2300 ft per second.

They dont, its a matter of what people like to a certain extent; I have used a 200 gr 40 cal Shock Wave to take deer bear and boar with excellant results and it is also the flatest shooting to my knowledge. I sight mine at 3" high at 100 and it hits 4 inches low at 200 which is about as far as I care to shoot off hand.

That can vary from person to person, I want a well constructed bullet that will open but hold together and penatrate 15 iches or more, what groups best in your gun should determine what you chose from.

777 is popular and gives good velocity not quite as good as BH209 in my favorite gun with my favorite load there is 200 fps differance; the other big differance is the crud and the crud ring, plan on cleaning after every shot with 777 most of us have to there are a few that dont have to, but no one has been able to define why or why not. with BH209 you dont worry about cleaning between shots it is not only not necessary but you wil get better groups if you dont.

It sounds like you are talking about break in, that will vary with what you buy and what you do, I do not advise any one to do what I do. I take about 50 strokes with a tight cleaning patch with polishing compound on it that reduces the break in to very little. It may put a bit of wear on the barrel as some say but to me that is inconsiquental.

To add a couple of comment, the power belt was vary popular at on time that date back quite a bit before sabots.
You are better off to buy the best quality in guns you can afford some of the cheap ones are just exactly that.
In bullets you may not get what you pay for some expensive ones are out date buy much better ones that are not as expensive and then there are the all copper oneswhich are vary expensive and vary good its just that since you can only kill it dead you dont really need that kind of bullet for dear or boar but they may be advisable for Grizzle bear.
A number of things also depend on weather you only want to set up for hunting or if you plan on shooting it two or three times a week like some of us. Lee