If it's something like a redemptor dreadnaught, where there is an ETB and a multipart kit, that's great. A unique hero like Astrelia Soulbright is also great.
What I am struggling with in modern warhammer is when you have a unit that you want to have multiple of in your army, but there's only 1 kit, and it's ETB. I really can't stand the idea of having 2 of the same sculpt on the table. It's not fun from a hobby perspective, and it's immersion killing on the table.