Switching from US domiciled S&P500 ETF to Ireland domiciled equivalents

Hi all,

Context: breakeven between VOO and CSPX with monthly DCA is 10 years considering using Interactive brokers(IB) only.

let's say for example one starts to DCA monthly into VOO (For e.g) and some years down the road, there's a more cost effective method to DCA into Ireland domiciled equivalent ETF.

would it be wiser to
1. leave the shares invested in VOO over the years, start CSPX on the more cost effective method.
2. sell shares in VOO and combine all the capital gains into a new DCA for CSPX on the more cost effective method.
3. Amass 100k USD capital and continue using CSPX through IB to further reduce trading costs.