dMEV vs SRHRV

[calumm]

[Reposting in correct forum]

I need to replace the old fan in my bathroom, and I'm trying to decide between dMEV (trickle, with humidistat) and single room heat recovery. My house (ground floor flat) is around 1930, with un-insulated cavities (currently looking at insulating them, and also improving ventilation).

The main benefit of SRHRV is the heat recovery aspect. Additionally, the air coming in can be filtered.

However, I'm also trying to work out what the possible disadvantages of SRHRV could be, so that I can make a more informed decision. Here's what I've come up with so far:

1. More expensive to purchase.
2. dMEV would help to ventilate the rest of the house, by pulling in fresh air through trickle vents etc. With SRHRV, would this be reduced, as air is being replaced directly in the bathroom; and would there therefore be less ventilation for the rest of the house? 
3. Air coming into the bathroom, while partly heated, would still be cooler than the air already there, so this could make it cooler after a shower (some reports online mention this).
4. Clearing of moist air would be slower, as the fan is only extracting for 50% of the time (at least, for single-fan units which switch every 70 seconds or so). (Again, mentioned online.)
5. Might clearing of moist air also be slower because some of the air in the vicinity of the fan would be fresh air which had only just been brought in?

These are my speculations as to the downsides of SRHRV. Do they seem valid? Is there anything else?

Thanks - Calum