There’s a growing split in the way manufacturers handle storage expansion in their devices and with micro SD cards having reached remarkable price to storage ratios you probably need to consider very carefully whether that non-expandable phone is really such a good buy.
Here in New Zealand Apple charges an extra $200 to jump from the 32GB iPhone 7 to the 128GB version. A phone with 32GB on board and expandable memory can be upgrade with a 128GB branded Class 10 micro SD card for under $70.
Buyers of Google’s Nexus 6P fare even worse, paying NZ$200 to go from 32GB to 64GB of storage. That extra 32GB bought as an micro SD card will set you back under NZ$10 right now.
Now in the past the performance of the expandable storage has been called into question, however with most phones starting at 32GB on board, applications can be kept on internal memory and media, which is generally less performance sensitive, shunted off to the storage card.
Of course if you’re going with Apple there’s little option but to take the pain of the cost of the extra storage, especially if you consider the (lack of) capability in the iCloud service. For Android though you really should think twice before foregoing expandable storage.