Hi WannabeSLP, I am writing an undergraduate honors thesis right now. Honestly, it is a lot of work and a big time commitment. However, it is a rewarding experience, to know that you are adding knowledge to our field! I think it depends on what you are interested in. If there is something in this field that you love enough to dedicate a lot of time a effort on then I would say go for it! The key is making sure it is something that you are genuinely interested in.
Also I was wondering if for grad school if you choose thesis option, do you still do a clinical externship? I would not want to miss out on the clinical aspect!!
Hope this helps a little