Suggestions for iPhone models to replace an old iPhone X

Apple's Certified Refurbished store currently contains iPhone 14-series and 15-series phones.

There is a tool on Apple's site that you can use to compare the features of nearly all iPhones Apple has ever made:

Apple – Compare iPhone models

The regular iPhone 14 and 15 appear to be closest to what you have now in terms of size and features – but you can get more features on the Pro and Pro Max variants; or bigger screens on the Plus and Pro Max variants.

In terms of future updates, since the 15-series phones are a year newer, they'll probably receive future iOS updates for a year longer. The 17-series phones and the iPhone Air are at the very beginning of their update cycles, but you can't buy them Certified Refurbished; only new.

If you're planning to buy a refurbished iPhone, do yourself a favor and ONLY buy it from Apple. Buying a refurbished iPhone from anyone else, is risky and you may wind up with a poorly refurbished phone, which has issues. Buying from Apple gives you peace of mind knowing the phone has authentic Apple parts and comes with a one year warranty. See this link --> Certified Refurbished Products - Apple

We can't tell you which model is best for you. We don't have a clue how much storage you need or which features would be most important to you. You can use this link to compare the models --> iPhone - Compare Models - Apple

Finally, read this about buying used iPhones (a refurbished iPhone is a used iPhone) --> The All Too Common SAD Reality of Buying … - Apple Community

Buy a new iphone 17, simples.

pro means it have more cam lenses, max mean the display is bigger not sure if it's big enough for you to read without reading glasses though.