Most iPhone users are probably using Lightning to USB-A cables for charging and data transfer, especially since that's what iPhones and iPads currently ship with. The USB landscape right now is a confusing mess of several different specifications and protocols, but that will all be cleared up with the arrival of USB4, probably in late 2020. Whereas USB 3.2 uses incorporates both USB-A and USB-C connectors, USB4 will move completely to USB-C. If this is already confusing, it is only the tip of the iceberg. Suffice to say that USB-C supports faster data transfer rates, will be the future standard, and can be used currently.
There are plenty of Lightning to USB-C cables currently available. When it comes to cables there isn't all that much to consider - you want the right length for your needs (which is probably longer than the meager 3 foot cable that ships with iPhones), a cable that is durable and not going to split and fray near the connection points, and a cable that is going to work with your hardware. To meet that last criterion, you want a cable that MFi certified, which means it is approved by Apple and will work with your iPhone or iPad. If you are looking to make the switch to USB-C, here are some cables to consider (all of which are MFi certified):
Newest iPhone FAQs
Anker Powerline+ II
Anker is best known for its high quality power packs, so it stands to reason that they also make decent cables. Their Lightning to USB-C cable has a double-braided nylon sheath that is laboratory tested to withstand 30,000+ bends. It is 6 feet long and comes in red and black. The less durable (but still good for 12,000 bends) Powerline II comes in an economy 2-pack.
RAVPower offers 3' and 6' cables in black and white. It is one of the more affordable cables on this list but still laboratory tested to withstand 30,000+ bends.
Another well known brand in chargers/cables/screen protectors space, Belkin's 4' Lightning to USB-C DuraTek cable is protected by a nice looking white braided nylon sheath that makes it "10X stronger than standard cables." It also comes with a strap to tie the excess cable.
The most affordable cable on this list, UGreen's 3' Lightning to USB-C is nylon braided cable that is a cheaper replacement than Apple's standard, less durable cable.