the best are obviusly the ones factory fitted, Low cost and economical,
the rest is upto u Jitna gurr dallo ge utna meetha hojaiga,
iridium, titanium or who noes i guess gold plated are also avalible..
btw my personal experience, every tym u get new plugs u feel a good change in the pick may it be 1 pins or 4 pins,
4pins have a longer life, while 1 pins have a short life.
as for price i got bosch 4 pins a while back RS. 1200 for a pack they were avalible for RS. 900(set ov 4) but i had to pay thru credit card so bought them from a expencive shop
and when the car went for a tuning to Suzuki, they gave suzuki genine plugs for RS. 980(set ov 4) from SUZUKI DEFENCE,
they were normal NGK 1 pin which are avalible in the market for 470 (4 peices)