I have been with the 25-06 since back in the late 80's. I got one specifically to have a flat shooting round that I could also utilize the huge pile of 30-06 cases I had accumulated from many range range visits. What I found was almost love at first fire.
I initially loaded it with the 100gr bullets in various brands, and with plenty of range time I had little trouble finding extremely accurate loads. Probably my best find was a load which shot the Nosler BT, and Partition, as well as the Barnes X, all within a group of less than 2" at 200yds. This was nice as I found the BT simply wasn't cut out for feral hogs where the Partition and X made for much better medicine.
This went along for about the first three years I owned the rifle, during which time I also played with several 117 and 120gr loads. Both of these weights were very accurate from my Rem 700, but there was just something that I didn't like about it. With the 100gr bullets I could easily hit 3350 within the book load data, but for whatever reason the others would start flattening out primers around the 3000fps range, and rarely break it without spread groups or high pressure.
When I finally found some 115gr Partitions, this all changed. I chose a load form the Hornady manual I was using for the 117's and worked it all the way up to the book max and actually hit the velocity they did with my loads and no issues what so ever with pressure. Running the 115's at 3150fps, the rifle thrived on them and accuracy was right back to the 1/2" or so at 200yds that the 100's had been doing. This to me was the best of both worlds. I had velocity, with a bit more weight. I used this load exclusively for the rest of the time I kept the rifle.
The year the 110gr Accubond came out, I had gotten my parts together for a custom 25-06 AI, and when I got it from the smith I stripped the older Rem 700 down and cleaned her all up and presented it to my daughter who had wanted it for years. I took the one box of Accubods with me to a friends where I simply swapped out the bullets from the 115gr load to the 110's. THe first thee shots at 200yds, we actually had to ride out to the target to see they all hit the paper. The group was three .257 holes in a clover. So I loaded up 20 of them, along with 20 of the standard 115gr loads and gave them all to my daughter to decide which she wanted to shoot.
It only took about three days before she said she would stick with the Accubonds after dropping her first buck with them at just past 250yds.
This was quickly followed up by a couple of hogs and a coyote while out checking a gut pile with the spot light. The yotes eyes were just glowing balls in the scope from what she said, so she put the X between them and touched the round off the first round just past 100yds.
The second night checking the gut pile, is when she got the hogs. The first one bit the dust at a little over 150yds and the second one faulted when it stopped at just past 200, where she repeated the process, while her fiance held the light.
Since '05, when I presented that rifle to her, she has taken several more nice bucks, mostly at 200+ yards due to the way our farm is laid out. The oldest grandson also got into the game using the same rifle, year before last on his 9th birthday. The daughter took this one two days prior,
and he then followed up with this one,
The cool thing about it was, the daughter took her first buck with the same rifle when she was 9 as well.
As for how the old shot out barrel is holding up after close to 25yrs of top end loads, well I shot these two with it on a very windy day at 250yds while checking the zero before last hunting season. The oldest grandson and I had been shooting up some older loads and I had just cleaned the barrel. I fired the one fouling round, (low), and then the following two.
While this would mean little to most who post groups, this is such a regularity from this rifle, that it is all I need to show me things are on par for it. It is actually sighted in at 200yds and with the wind gusting that day I didn't mess with the scope what so ever. It has shot like this with most loads I have worked up for it, since back when I first put it on paper, and if it doesn't, it isn't the rifle or the load.
To be totally honest, if you go with the 25-06, I would simply go with the 115gr Partition and be done with it. I have personally found that while the 110 Accubond is great for deer and smaller hogs, the bigger ones can easily soak up a good hit and with the hide and fat they leave little to no trial when they hit the brush. The 115's, I found like the 100grs above in BT, X or Partition, always did the job no matter what. I have used for the most part the Partition, on plenty of whitetail deer out to just over 400yds and a 250# mule deer at 40, with equal results, usually dropped in their tracks or only made it 20-30yds before doing so. A couple of my favorite shots were a skunk at 283yds, and a yote at just past 350. The skunk was shot just behind it's bobbing head with a 115gr Barnes X, in about 8" grass after my good friend said there was no way I could do it, and the yote was looking around a bunch of tall Johnson grass where all I could see was half of his head. I hit him just under his left eye with the 115gr Partition, while aiming right between them from a slightly rocking tri-pod stand.
Good luck with your purchase what ever you go with. If it's the 25, and your working up loads there isn't much better stuffing for it that RL-22 for the 110gr and up bullets. For anything less I would look hard at IMR-4831. These two will or should give you the best velocities within the load data that you will get. As for the best barrel length, well the one mentioned above is the stock Remington 24", and it has been well used, and is holding up fine. While the shorter will give decent velocities the 24 isn't overly cumbersome. The 22" will give you decent velocity, but you will also get plenty of muzzle blast as well. Not to say the 24 doesn't provide that but the extra 2" seems to help make it not so obtrusive.