From my experience, letrozole is more able to induce ovulation than clomid, and with fewer side effects.

I only ever tried clomid once. At 50mg I failed to ovulate and had such severe anxiety attacks during that cycle that no doctor was willing to ever let me near it again.

I used letrozole on several occasions to induce ovulation in order to do a natural FET as part of my IVF. If memory serves correctly I was only taking 1 letrozole tablet, and I can't even recall which days of my cycle I took them, but I managed to ovulate every single time. I had five cycles all up - three were positive but resulted in miscarriages (not due to the letrozole, due to several other health conditions I was trying to juggle), one was negative and the final one, my last embryo failed to survive long enough to get to transfer so it never happened.

The drug is used as part of fertility treatment much more often in the US than here. It's not technically approved for use in fertility treatment here (or at least it wasn't when I was using it around 2 years ago), but from my experience it works quite well. The only side effects I had were hot flushes while taking the tablets and very mild anxiety leading up to ovulation, but that's just a unique thing my body does in response to elevating estrogen levels.

BW