Difference between Lookup fields and Javascript fields?

[Brandon M.]

Title is a little generalized, but specifically speaking is there any fundamental difference in how the Gui Lookup field works verse using a Javascript field to do the same thing with field("link to entry")[0].field("field1")?

In some of my testing to reduce entry load delay for users out in the field (team account, large libraries), I've noticed that Javascript fields don't appear to take as long to load as Lookup fields. I had a bunch of lookup fields in my test database, way too many for real world application imho but there were about 30 of them. I noticed that it was taking ~1-2 seconds longer to load an entry  with 30 lookup fields vs 30 javascript fields setup to do the same thing.

Do Lookup fields have more overhead? Do they execute before the entry is rendered and javascript happens after the entry loads? Is there any explanation for this noticable discrepancy in load time?

I've already switched my design style to avoid excessive lookups and network calls, but now I'm curious as to why this is happening or if I'm just imagining things from less than perfect testing?

Thanks in advance,

Brandon