Personally, I recommend both a microchip and a tracker of some sort (either GPS or radio-tag). A GPS and radio-tag can help you track down your missing cat within a short time. For a microchip to help, your lost cat must be caught and then be brought somewhere to be scanned for their chip. Since lost cats may be loose for days, weeks or months before being caught, a tracking device will help you find them much quicker. However, trackers can have problems – most commonly the battery may not be properly charged or they can come off the collar. For this reason, I would also recommend a microchip as back-up. When all else fails in your search, a microchip may still bring your cat home. But it could be a very long time. You can learn more about microchips here: https://lostpetresearch.com/2019/11/is-your-pets-microchip-working/