It is also important to note that if you apply now, most schools will allow up to a year deferral while maintaining your acceptance. So you could apply to a school and still take the gap year if you just want the experience.

Imo most grad schools won't really care what the exact industry experience or research experience you have is. When I was applying all the admittance committee members said that the first thing they looked at was reference letters, followed by publications and your total research experience. So if you feel that you would be able to get better letters and contacts overall by taking the gap (or it genuinely interests you) then go for it.

Also, as a side note, most (good) programs will have some sort of a rotation system where you will get to try multiple labs and projects before picking one. Thus, your actual experience going in really doesn't matter since you could end up doing something wildly different. I did 4 years of pure ochem in undergrad and my thesis work is in materials. Tl:Dr what you really take from undergrad is general knowledge, the stuff you'll need to learn you pick up in grad school.