Tube preamplifier tube choice help please


I would like to ask which tube is better linearity and sound among 6SN7 and 6NP1 tubes in preamplification or what are their pros and cons
There are two brands tube preamplifiers I intend to buy they have almost same topology, one uses only a pair 6SN7(Tungsol) and the other one uses only a pair 6NP1 (Russian) they both have
tube rectifiers and roughly same prices
I have not used those tubes in any application before so I would like to hear your comments please.
Thanks in advance
ben
I have Cary SLP 98.

I tried few 6sn7 tubes in the front and always have sylvania gtb at the back.I tried tungsol brown base,sylvania brown base and few more and sound really good..Then I tried these 6sn7 tubes from russsia with a 1578 stamp on the glass ...then I stop looking for more 6sn7 and always happy listening to music now.I recommend these tubes to all A'gon member who own a Cary Slp-98 pre-amp and what a difference.Please try it!!Don't ask me now how it sound but i do believed you will be happy with this tube especially mate with cary slp-98.
the russian 1578 tubes, if genuine, are exceptional. i use them for input and sylvania bad boys for output on my wyetech opal pre, after much experimenting, and it is a great combo. ken-rads add more warmth if you like that. 6sn7's are widely available and offer many tube-rolling opportunities to get the sound you want.

neal