ml320 plugs

[nisan17]

Group, I know the topic of plugs has been brought up before, but I want to clear up why certain plugs are recommended so I won't won't feel like I did an inadequate job or spent too much money on plugs that a cheaper plug could have sufficed.

While having my ML serviced by an experienced foreign indie car shop, the tech brought it to my attention that the plugs were pretty worn and I should have them changed before winter sets in. He stated that I need to get my plugs from him as he's the only one that has them...at $10 something each.

My guess he's speaking of Bosch's #FR8DPP33, $10.86 online.
Why couldn't I go with the lesser Bosch plugs of: #4301 @ $4.99 or #4418 @ $5.18 or #WR8DCX @ $1.44 or FGR8DQP @ $6.19?

The local auto parts store has #4301 listed for my 98 ML320. I've noticed in other posts that owners have used #4418 and the older #FR8DPP332.