People who say that camo does not work in airsoft do not understand what the full purpose of camouflage actually is. Yes it is intended to help one blend into the average background of the terrain one is in, but that is in not its only purpose, it has several others. These being, recognition of friendly troops so you know who is whom and don't engage your buddies, and aiding in delaying target acquisition and range finding, by breaking up recognisable outlines, the latter being perhaps the most important factor.
A classic example of the latter, is the splinter camouflage found on many WW1 and WW2 battleships; nobody was seriously expecting those paint jobs to actually hide a battleship, but they knew that when enemy gunners looked through their scopes at ships painted in such a way, it was considerably harder for them to determine the type of ship, its length and height on their stadimetric rangefinder scope reticules, because the pattern was breaking up the vessel's outline, so they would be slower in sending accurate range data settings to the guys fusing the shells and adjusting the elevation of the guns. The well known saying, 'thrice blessed is he who gets in the first hit' had a real meaning for the people in those old battleships painted in schemes which made enemy gunnery more difficult, since one accurate shot before the other guy could even fire at all, was often the deciding factor in a battleship engagement. The same is true in airsoft much of the time; all other things being equal, it's often the player who fires first who is going to win the engagement.
So, when it comes to picking a camo scheme which you hope will work in two environments, you might find the criteria of 'what works against the typical background of the terrain' cannot be suitably addressed, but the other two criteria of 'recognition between friendlies', and 'breaking up familiar outlines', most certainly can. Because of that, I would suggest that a scheme which breaks up outlines more effectively on the more open ground would be the better choice, since that is the one where there will be more opportunities for snipers, and anything you can do to slow a snipers's process of spotting, determining range and taking a shot, will pay greater dividends in that terrain than it would in other locations where the sniper ranges may be closed down. You may also consider what people you regularly team up with are wearing as another criteria which will aid in teamwork, but since that is not something which can be entirely relied upon, I'd say it was a less important consideration.
It's worth noting here, that one of the main issues with all camouflage, is that generally speaking, it tends to be a too dark to work at longer ranges, where terrain colours fade with distance, so that's something you might want to consider too, i.e. you may well find that a desert camo, whilst not being the typical colour you'd find in most quarries, is at least not going to be dark against stone colours which are being illuminated by a lot of sunlight.
