Is there any considerable advantage to a forced air-to-air heat exchanger over just cleverly positioned positive pressure forced air intake?
This is a simple question requiring a complex answer...!
What you are asking is the cost-benefit tradeoff of installing a heat exchanger. How much will you save on heating costs, vs what does it cost to purchase and operate the exchanger. And you wish to compare that to forced air ventilation.
Factors to consider:

Required or desired ventilation rate, usu. depends on occupancy and your tolerance to flatulence
Number of heating degree days, from local climatological data
Heat exchanger efficiency, e.g. 60-80%, or 0% for ventilation without exchanger
Electricity consumed by exchanger, including its fan and defroster
Cost of heating, based on your local price of electrical or hydrocarbon energy
Purchase cost for the heat exchanger sized appropriately for your dwelling

This linked article shows a pay-back time of 5-years, but of course, it all depends on your parameters. The data in these calculations use imperial units, but it's a good example. You'll find similar calculations elsewhere, and I wouldn't be surprised if your local energy supplier has some detailed data, considering the cost of energy and your climate (Belgium? Netherlands?)
https://home-energy.extension.org/cost-effectiveness-of-installing-heat-exchangers/
Personally I have found that in mild climates (North West Europe, Western Canada / North Western USA) the heat loss due to cracked-open windows or natural ventilation pales in comparison to the house's heat lost through building envelope cracks &amp; radiation losses. The heat exchanger makes much more sense in areas with long winters down to -10C ... -20C.
One reason is the obvious temperature of the taken-in air, but the other is the local building code for insulation. Milder climate regions often have looser insulation requirements, and so the total energy loss is less impacted by ventilation.