Well.... Cold starting should not really be dependent on glow plug type, but engine condition, proper maintenance, proper winter fuel and oil (in EXTREME climates) and so on. That said, either plug style gets the prechambers as hot, but the pin style plugs heat them in less time. The loops have a reputation for being more robust. The rare series loop plug failure can be a bummer, though, since they are in SERIES, and when one fails: no glow. A parallel pin plug failure will at least leave you with some glow. The general consensus is that pin plugs have a higher - perhaps even routine - fail rate. I'll encourage you to do a search of this forum, key words "cold start" for a wealth of information on the matter from folks who live in really, really, cold places. I'm in northern California.

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'78 300D 310K Maple Yellow / Bamboo
'87 300D 81K Barolo Red / Safron (RIP @ 113K)
2003 E320 34K Pewter/Charcoal
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