ETFs in Different Currency (URTH and SSAC)

Hi all,

Just want to check with you guys something. Hope you guys are able to help me. I been wanting to invest in the MSCI World index for a while. Want to do it through FSM RSP since it's the most convenient. However, I am not sure which ETFs to get. There's URTH, and SSAC. Understand that SSAC is under LSE, so there will be lesser tax. However, the currency is pound. Whereas URTH is USD

Is there any difference between this 2? Which is better? Seems like USD would be a safer choice as pound has been depreciating alot more over the years against SGD. So assuming the returns for both is the more or less the same (reinvesting the dividends from URTH), URTH seems to be better? Any advice? Thanks.