ARC LS7 vs LS16/I

Actually the LS16MKI uses (4) 6922 tubes and is a pure tube
preamp, like the LS7. The LS16MKII uses the (2) 6H30 tubes.
According to the subject title, the OP is asking about the
MKI version

I have owned both versions of the LS16. I found the MKI to
be more tubey sounding and the MKII to be faster, cleaner,
but more solid state sounding. I have never owned the LS7,
but have heard it. It's a pretty nice sounding unit.

I'm not sure the LS16MKI would be that much of an upgrade
over the LS7. If you could sell the LS7 and add a few
hundred dollars to get the LS16MKI, I might consider that,
but I wouldn't pay a whole lot more for it.

You might consider saving up and stepping up to the LS26.

For the record, the advantages of using a jfet input are many but the single most important advantage is the decrease in noise. Comparing the SP-16 an all tube preamp and the SP-17 with its jfet input, you will find the SP-17 is almost 10dB quieter! That is huge. With the phono stage installed it's the difference between having to use a 2.5 mV high output moving coil because of noise, and a moving coil that's in the .7mV range. More cartridge choices and much less noise, therefore a rather substantial difference. The use of the 6H30 tube, because of it greater voltage swing, ( it draws more heater current) greatly improves dynamics and transient performance over the 6922 or the 12AX7. The bottom line is the fact that each person's hearing and audio systems are different, it's best to listen to a preamp, if possible, in your own system in order to evaluate it's performance. There is no right or wrong choice.

Agree with hifigeek regarding the need to have quiet gain for phono stage.
Disagree when it comes to a 15 to 20 dB gain line stage.
But it's just me.

so you're saying that a 6H30 based preamp would be preferable under this respect, as far as I don't have a 15-20db gain in the line stage ? did I get it right ?

I was referring to hifigeek's comment about the advantages if jfet input/ first gain stage. It's quieter than tube implementations.
But if its line stage and not phono I never ran into a case where I think a jfet line stage sounds better than all tube.