I notice flavorings go bad (loose strength/potency, loose notes etc) much quicker in soft LDPE bottles, like in a year or less sometimes. Probably partially due to easier escaping of the flavoring via evaporation, and some notes probably get absorbed into the bottle too. Leeching plastics over time is also more of a concern with LDPE.
I agree, in some ways the LDPE bottles with tiny tips are good for mixing, but other ways they are not so great. It's a tough thing to decide on which bottles, both ways have benefits and negatives, and not everyone will ever be pleased with either/or.