tl;dr: More expensive, better returns and more conservative.
There are two ETFs for STI. In comparison, SPDR STI ETF has lesser expense ratio (0.3%) and smaller annualised tracking errorm so we'll just be comparing with SPDR STI ETF.
Management fee for Phillip SING Income ETF is 0.40% p.a, excluding other fees such as index licensing, trustee and auditor fees, etc (capped at maximum 0.7%). The top 10 stocks in index are similar to those in the STI ETF however the weightage is different. STI weights the stocks based on market capitalisation whereas Phillip SING Income ETF weighs it using their composite factor scores. STI sector allocation is 57.23% Financials, followed by 11.95% in Industrials. As for Phillip SING Income ETF, it comprises of Financial Services 31%, REIT 24% and Telecommunications 17%, which is more balanced and conservative since REITS and Telecom gives steady flow of dividends.
SPDR STI ETF has 10 Years Annualised of 8.44%, compared to Phillip SING Income ETF of 9.6% (2005-2018).