Probably the main difference between "new" and "old" is the addition of comparative passages in RC. The free June2007 is the beginning of such change. So anything PT's starting with Pt 52 (in addition to June2007) has the comparative reading.
They are pretty ok... should be used as a last resort though... so I would suggest saving them till may/ June... the first one you would have done... its basically June2007 all over again with Indian names... the others I think are different.
@emli1000 well i've alreadytaken the 50s PTs, so i'm just wondering if i should use them for drilling purposes instead of the earlier ones, to become more "fluent" with the newer tests? i could be overthinking this :)