Well you are comparing a mail order tune to a programmable ecu.
Of the mail order tunes Id pick Jim Wolf Technologies or RS-Enthalpy.
But for 30 bucks more than a mail order tune ECU you can have a fully programmable one.
Megasquirt has a DIYPNP ECU for s14. Head over to KA-T.org if you wanna get some real facts and real reviews from people who use both systems.
DIYPNP JECS 88 pin (Nissan) Unassembled Kit DIYAutoTune.com