The Dutch Army of 1914 was on par with other amies at the time. The big question is how much time the Dutch have to prepare the Waterlinie.
I would indeed imagine that man for man, the soldiers and other units of any Western European nation were quite comparable.
The issue is, the Germans massively outnumber the population of both Lowland nations combined. The Netherlands jumping of their own will onto the Entente bandwagon does not strongly tip the balance against the CP. OTL the CP wisely did not attack the Netherlands either. But if they did, while they might divert so much force from other fronts against stronger Entente members that they jeopardize their standing there, there can be no doubt that aside from the difficulties the Waterline present them, they will steamroller the Dutch forces to that line--by sheer numbers if nothing else.
As for the Waterline, would not its effect be that the majority of productive Dutch citizens are overcrowded in a small fraction of the Netherland's western territories, leaving a portion of their east perhaps deserted but owned, for what it is worth, by the Germans, and between them a goodly part of the productive land and industrial plant submerged and useless? If Netherlands and Germany go head to head, I do call denial of a major part of Dutch assets a win against Germany all right--but man, what a Pyrrhic victory that would be!
And the Germans anticipate this if they are sane and therefore do not attack.
If the Germans leave the Dutch alone, what motive do the Dutch have to bother the Germans? Other than Britain and France begging them to of course--but the Entente powers can plainly see that any Dutch hostility to the Germans spell their swift doom, at least to be beseiged behind the Waterline--and what good are the Netherlands as a beach head against the Germans, if the Entente lacks the manpower to prevail on the fronts they already have, and now must fight past the same Waterline that is holding superior German numbers at bay? The main thing the Entente needs out of the Dutch is for them to stop trading with Germany, but if they stop trading the Germans have less to lose and more to gain by attacking.
And there is only so much arm twisting the Entente powers can do, even though Britannia rules the waves, to force them to comply with Entente wishes--for another option the Dutch have is to throw in with the CP. This is a terrible option for them since they'd be as cut off from world trade as the Germans and probably lose their colonies (mainly DEI matters) unless the CP can force such a painful situation on Britain they are persuaded to trade colonies back. But the point is the Entente cannot bully the Dutch into joining them either since applying their worst case leverage would mean the Dutch have nothing to lose, but perhaps something to gain should the CP win. And at any rate they can augment German numbers and facilities.
Stipulating the Dutch join the Entente side is just incredibly far fetched IMHO, and makes very little difference to the overall conduct of the war.