Which fluid should I use

I've used both. Still own both. There are some differences. I use them on a vpi 16.5 with the disc dr brushes...like you seem to be.

Disc Dr-Takes 3 cycles for me. One with the cleaning solution diluted. some scrubing like they recommend. 2 rinses with distilled water. Results-lowers static some, queit-black backgrounds, some softening of the highs. Which can help is system is slightly bright...

Record Research-2 cycles, quicker cleaning. Seems to bring out more tranparency, more delicacy to the sound. Quiet black backgrounds.

Both bring out tremendous gains in sound. ie, you are not going wrong with either. The sound diff I hear are slight-not monumental.

Are you using the wash or deep clean? If you use both do you have a seperate wand for each process.

I use RR fluids exclusively after trying most all of the commercial brands and several home-brews. RR proved the very best and for most of the reasons Jfrech notes, especially in terms of it leaving NO sonic signature. I do use a separate brush for the deep cleaner and one each for the two passes I give with the wash. It may be overkill, but I rarely have to give a second wash to any of my LP's after employing two "rinse" cycles using my VPI 16.5.