EIS & SEIS [1] tax breaks for UK angel investors are a strong argument for the UK. Also R&D investment has tax credits too, so startup salary spend on new product dev is treated well by the UK tax office [2]. Don't know if PT & NL offer any similar breaks for startups & their investors.
[1] https://www.crowdcube.com/pg/seis-tax-relief-42 [2] http://forrestbrown.co.uk/rd-tax-credits-explained/