Hiya,
I might have been in a similar position, I got HEO from an internal competition, was in the position for 5 weeks and then got the AO from the open. I took the AO. Partly for the kudos (open v internal - the internal competition from which my replacement was selected had 6 applicants for 2 posts whereas the open, as you know, has a cast of thousands) and partly because the HEO post was decentralised and also because, god knows, a change is a good as a rest!
The basic advice was that it depends of the work you are asked/expected to do. At the same time most of the people whom I told I got the AO congratulated me (although they knew I was a HEO). Even when I gave "notice" I was congratulated by the very people I was leaving in the sh*t!!!
Of course I will carry over my HEO salary
. I will try to carry over the HEO annual leave too. The AO increment is double that of the HEO as you probably know.
I've wound up in a position (in terms of work) where it may make no odds what the grade is, in fact my APs didn't even know I was an AO and presumed I was a HEO (as that was the grade I was replacing). It will be interesting to see if they will make a difference...
In fact I have the best of both worlds, AO cachet and HEO street cred, not to mention HEO working conditions....
I hope to get the "year out" but as you may know, word on the gripevine (sic) is that they are doing away with that. I hope I get to be one of the last.
My overall impression is that the difference is dead. AOs used to be the cream of the crop, the fast track, the "groomed for management", some made AP in 2 years. But that was in the days when the majority of COs didn't have PhDs! It is true that to want to be an AO is to have ambition, and some HEOs are at the pinnacle of their career. Between some HEOs and (god knows) some AOs there will be no difference, you have to make the difference yourself these days. Some AOs god love them fu*k up madly, esp. in staff management but you sound like an experienced EO+ so you should be able to handle that, so be an AO but act like a HEO towards staff, if you have them.
My advice, take the HEO and THEN the AO if you can!
Good luck!