I use a MK saffiano leather makeup bag. I've used it everyday for a year and still looks brand new. I was going to buy a LV one but couldn't justify it since the MK one is just good quality. I got a toiletry pouch 19 to hold odds and ends in my bag so that way if I do ever really want a LV makeup I have one but just not the same shape as the MK one. Lol makes sense to me. Sorta. Haha
If I were to buy LV, I prefer the TP better than the makeup case. I would also go for the 15, I just want a small, compact case and I don't carry a lot of makeup. But it's ok for me to buy the cosmetic case shaPe from another brand, so in the future if I buy a TP I will have different styles. I totally get what you mean. Lol. I use an old version pochette to hold odds and ends too.