Thats a terrible analogy ! How does being invisible require any training ? How is being given extra durability require any training. Beside all of that it is undenible that the raid suit is a much better power up for anyone . So many new ability that was previously impossible. Enma is just a mean for greater strengh, it does not give devil fruit like abilities.
Well, you are not only invisible for others, you can't see your body either. Imagine failing to block an attack because you don't see your leg where is heading to lmao.
The suit does not give more durability, it is flexible, they are clothes. The impact of any attack Sanji would feel them with his own body, he needs his own durability to tank the attacks. Suit gives the extra of being resistant enough so for cutting/piercing attacks it can stop the pierce, that's true, but not the impact/energy behind those attacks. And anyway, Sanji can take those kind of attacks with his Armament. The shield cape is the only thing that gives actual durability.
Enma does not give greater strength, a sword power depends on its user power. Enma's power up consisted on Zoro's training his Armament Haki. Armament = power and defense. That is above suit's "durability" or power increase. Haki is a more efficient way to boost your power and defense than Germa's technology.
And Sanji's invisibility probably will have some sort of limitation, Oda does not give good abilities without a handicap or some kind of limitation for free.
So their PUs are similar.