You will not be able to carry anything on bed rails...rear of the sail panels are only lids to the saddle storage bins...they would be damaged if any significant weight was placed upon them
I have two avalanches...a 2002 and 2013....the 2002 has a bullet proof 5.3L all cast iron....with 250M miles and all I have done is replace the plugs, wires and belt....the 2013 RWD has aluminum heads, which can be a problem in an overheating event.......in the later years, the 4x4's have an all aluminum engine which addresses the added weight by the transfer case....I would prefer the cast iron engine...
I think the best thing to happen to the Avalanche was the 6 speed transmission...maybe the worst was the 'Active Fuel Management' system...this was also known as 'cylinder deactivation' first introduced on Cadillacs decades earlier....it represents a lot of computer driven technology and parts to gain only appr. 7% savings/advantage (I don't recall where I read that)...can't really assign a negative factor to this AFM because GM has kept a tight lid on it somehow....however, a whole after market industry has developed with the purpose of disabling this feature and re-tuning the computer and making customers happy...
In my case, I don't find it significantly objectionable...but my 2013 never goes into 4 cylinder operation unless I am traveling downhill with the wind under 70 MPH....that being said, it appears that the gains are minimal but necessary to get passed EPA mandates.
If Avalanches didn't exist, I would have to own a truck and a SUV in its place...I can travel and pull into a nice hotel with valet service as well as drive onto muddy job sites and work out of it...I regard it as the most versatile and utilitarian vehicle ever made...my wife quickly grew accustomed to the size and height/visibility aspect and neither of us can tolerate sitting in a car with our butts less than 18" of the pavement eye level with the bumper of the vehicle in front of us.
IMHO, when shopping for a low mileage, clean, well kept Avalanche, you will discover the relative highest resale values in the used car business. This would be a testament to strong favor-ability but in a small market and an ever increasing rarity...it appears that GM will not bring back the Avalanche...I waited years, thinking they would...I got a good deal on my 2013 and think I can drive it with moderate mileage for 2 or 3 years and sell it for what I paid.
Tip: The narrow market is the buyers only advantage...I found a 'trade in' Avalanche at an exclusive Lexus dealership...they didn't have the kind of traffic to move it off the lot...after 50 days it went below wholesale and advertised on Ebay...I was first at dealership on a Monday morning with 'note lot' dealers back of me...I didn't have much time to check it out and the sale was "as-is". I wrote the check and anticipated the worst...pleasantly surprised, the only expenditures to date are upgraded (2" lifted) Rancho struts and shocks, an Apple-play radio, plugs, wires, and front brake discs...none of which were critically necessary...the owners did sneak a cd Bose replacement for a DVD Bose that went undiscovered by all parties...but I am going to replace it anyway....the 2" lifted struts are necessary if considering any larger wheels/tires in the future and gets rid of characteristic factory slant.
Hope this helps