DOL Starter or a Star Delta Starter

DOL and Star-delta are both available. But the choice depends on

1. whether your utility from which you get power, will permit such a large inrush current when you start DOL.

2. whether your mechanical load can withstand the high starting torque that DOL starting gives.

3. whether your load is ok to be star-delta started ... (ΥΔ gives only 1/3 torque as compared to DOL)

If you can afford it, use a Softstarter. ΥΔ is not really a good choice.

As much as I detest Star Delta as a starting method, whomever told you they don't go to 500kW was very ignorant, or very selfish*.

*There are a few control component manufacturers who specialize on only making the highest volume products at the cheapest possible price, so they concentrate only on small controllers. So if you only make contactors up to 200A, you cannot put together any combination of your own devices to make a 500kW Star Delta controller. If that's the case, the person you spoke with was being disingenuous.

All that said, I prefer solid state starters of Star Delta 100% of the time. Star Delta starting, as evidenced in the above graph, simply trades one big hit for 2 smaller ones, and the consequences can sometimes be worse.

By the way, are you hoping that by changing the wording of your question you are going to get a different answer?

Please give the forum a clue as to what voltage it is dealing with!

Neither of them.

Have you considered Auto Transformer Starter with Korndorfer Closed Loop Transition?