The MK and Burke low F are both very good whistles, which I consider on opposite ends of the spectrum from each other. I don’t think either is a bad choice, though. I own both, and both are great.
However, I also have an MK and Burke low D, both of which are also great. However, I also have a Reviol low D. In my opinion the Reviol low D is better than either the Burke or the MK. I have since ordered a Reviol low F, which has not arrived yet. This week I’ll be able to chime in about the Reviol low F. I can say the low D Reviol is very very highly underrated, in my opinion.
If the Reviol low F compares to the Burke and MK low F’s the same way it compares to the burke and MK low D’s, I’d without a doubt give the Reviol my recommendation. However, it hasn’t arrived yet, so I have yet to find out.
I find the MK seems either the best, or the worst, whistle for the job at times. It has a very unique tone, which I find either very fitting, or very un-fitting for certain tunes. The low octave is a very heavily smokey tone, with an upper octave with a very high degree of attack on the notes, which I find somewhat intense, at least when I play it. Sometimes I find those qualities a bit too much for what I’m playing, in which case I would choose the much clearer sounding burke. Both are great whistles, though. I don’t prefer one over the other, overall. Both are very responsive, and with good volume.
The goldie low F is amazing. The single thing I did not like about it, is that mine had way too much backpressure for me. I prefer nothing more than a medium amount of backpressure in a whistle, and mine was a harder blowing whistle. Were it not for that, I’d have kept it. However, I bought mine used, and colin will make it to your specifications, therefore you are almost guaranteed to have an awesome whistle if you order with him and communicate what you are wanting in a whistle.
Therefore, I’d have to second all of the recommendations given so far, except for the chieftains and dixons, which I haven’t played. The dixon tapered bore plastic low D is very good for it’s price, though, so I imagine it wouldn’t be too bad in F either. I don’t imagine it would stack up to par with a burke, MK, goldie, or reviol, though. Could be wrong, though.