Matching JFETs for differential amplifier application
To be on the safest side both \$I_\text{DSS}\$ and \$V_\text{P}\$ should be checked and matched, it is well known that those two JFET's main parameters usually spread widely.

What is less known is that they are strongly correlated, at least for same manufacuter and lot.

A look to this \$I_\text{DSS}=f(V_\text{P})\$ scatter plot done on over 200  different JFET may clarify

( source viva-ananlog.com)

matching for \$I_\text{DSS}\$ will most likely accomplish good \$V_\text{P}\$ consistance too, and viceversa.

Then you have to known your circuit requirements, how much unbalance you may tolerate and eventually include some trimming if not confident.