I don't think it would matter too much over here. I prefer to tilt mine down as people love walking into/knocking the skeg when it is tilted at 45 deg angle. I know in countries where it freezes in winter they advise the down position so any water in the motor can run out, this prevents any water in the motor freezing and cracking things. Another reason I store it tilted down is it takes less room. 6.1 m boat + trailer + outboard tilted at 45 deg is pretty long. Never had any smoke issues when starting

The oil is in a sump under the powerhead.. It can't go back up into the powerhead..(unless gravity is playing up again.. Damn gravity!) Perhaps if it was stored tilted all the way in (past vertical) a bit of residual oil in the bores could leak past the rings..

I think on balance its better to store vertical so the cooling system drains out.  Cooling system corrosion or salt accretion seems more of a risk to me than small amounts of oil sneaking past the rings.

A 4 stroke petrol engine can last along a time with oil getting past the rings ...

I think its crap too, had one guy tell me that a yamaha rep had told him to only use the flushing port when he got his motoer home, as it didnt run hot enough to oil it all up inside the motor...sorry but i will always run mine at home in a drum, want that salt gone and the thermostat to open.
plus.... as said up there,, a tilted outboard skeg is a nasty surprise for a kid to run in to...

I dont know about 4S outboards... except when storing a vecile type 4S one sets it up right so the oil in the crankcase doesnt get into up into the cylinders, and or the oil pump get exposed. The latter if left long enough may not prime as the engine turns over resulting in turning over firing with no lube and dry cylinders.
 Cooling draining... again dont know how 4S  a cooling galleries/ ports are set up But on a johnson / evinrude the Service/ Repair manual recommends storing vertical so all the galleries can drain dry, preventing internal corrosion.
And if wintering...to blow the galleries, in particular the speed ports with air.
 I would think it safe to ASSUME a 4S cooling galleries, impeller, pumps, ports etc to be similar to a 2 S.

The caution in doing this is leaving down, forgetting and moving the trailer, hitting the skeg on the ground going over a bump. 
Another issue is if uncovered or no engine cover is water in a storm going in thru the vents and laying inside around the power head... even left upright in a heavy  wind storm.

 And a side note on storing carbed @stroke tilted...the oil and gas drains out of the back of the carb... leaves oil around the base of the powerhead... I dont think that is a bad thing.
With most of the fuel /oil mixture drained out of the carbs, and fuel evaporates, it may tend to leave the carbs dry.. which in long periods between use may cause corrosion drying of gaskets etc in some engines.
Left up right leaves a oil in the carb... but will smoke up when 1st fired for a minute or so.

If not using the engine for a while.. any engine, vintage car, rod etc.. winterize it... gets a bit messy when re use but worth it .. no stuck rings, lubed when fired up etc.

I always thought 4S were supposed to be stored in running position, as in vertical, outboards, mowers, cars, bikes, anything 4S.

4s mowers are not recommended for hilly sections, as the oil all goes to one side of the shallow sump, and they run dry
plus they tended to be heavier