First of all, an important advice: if you plan to apply the NFC Tag on a metal surface, it is necessary to use the On-metal NFC Tags, otherwise the metal surface will interfere with the magnetic field of the chip, making it be unusable.
After this clarification, which can be applied to all types of NFC tags, you have to understand if your project requires NFC Tags compatible with all devices, or if this feature is not necessary.
NTAG SERIES - COMPATIBILITY WITH ALL THE DEVICE
If you need NFC Tags that are compatible with all smartphones and tablets equipped with NFC, then you have to choose the NTAG chip. There are different types of NTAG chips. On Shop NFC, you can find NTAG203, NTAG212, NTAG213, NTAG215 and NTAG216. Here are the main characteristics of each of these chips.
NTAG203 is a great chip, widespread, which has a capacity of 137 bytes and is available in different sizes, shapes and dimensions, as well as bracelets, pendants, etc. In general it is great for any use, even if it's being replaced by NTAG212 and NTAG213, the new generation chips. Go to NTAG203
NTAG212 is more advanced than NTAG203: it has better performance in terms of reading speed and range. It has a slightly smaller memory, equal to 128 bytes. It has the considerable advantage of being less expensive. If you do not have particular needs, this chip is perfect. Go to NTAG212
NTAG213 is the new generation of NTAG203: it has better performance in terms of reading speed and range. It has a slightly bigger memory, equal to 144 bytes. It's quite cheap and it's a very good NFC Chip. Go to NTAG213
NTAG215 is in the middle between NTAG213 and NTAG216, because has an available memory of 504 bytes, so it's suitable to be encoded with V-Cards or more data. As all the NTAG21x, it has some more features, as the password-protection. It's slightly cheaper than NTAG216, but it's a very good NFC Chip. Go to NTAG215
NTAG216 has the advantage of having a larger capacity than the other NFC Tags, thanks to an available memory of 888 bytes. This makes it a great chip for business cards with very complete V-Card data. They are very fast, but are also more expensive. Go to NTAG216
MIFARE Classic 1K and ULTRALIGHT Chips - LIMITED COMPATIBILITY
If you do not have needs for maximum compatibility, you can also choose other types of chips, such as Mifare Classic 1k or Ultralight.
Mifare Classic 1k Chip
NFC Tags with Mifare Classic chip have a rather capacious memory, equal to 716 bytes available. They are recommended if you are already using a system based on Mifare protocol (as some access control systems), or if your Tags are not going to be read by general public.They are compatible only with certain Android smartphones. The NFC Tag Mifare Classic also support encryption. If you do not have the need for maximum compatibility, Mifare Tags are excellent, available in various sizes, shapes and dimensions. Go to Mifare Classic
The Ultralight NFC Tags are more advanced than the Mifare Classic and are compatible with BlackBerry devices, with almost all Android devices, and potentially also with Windows Phone smartphone (even if they require a special formatting). They are quite cheap, but have a very limited memory, amounting to only 46 bytes, which makes them useful only for short links or for short text strings.
In any case, before you buy NFC Tags with Ultralight or Mifare Classic chip, please check the compatibility of smartphones and tablets with the different NFC chip.