Should I be purchasing the VUSD since it is performing better than the IWDA, although it does offer higher risks?

Like what Brendan mentioned, the underlying index that both ETFs are tracking is different. Unless you're comparing something like IWDA and VWRD.

VUSD is tracking the s&p 500 and has a TER of 0.07% while IWDA is tracking the performance of the MSCI world index and has a TER of 0.20%.

Choose if you want a more diversified ETF which tracs the world index or one that just tracks the performance of top 500 companies in the US

I'm assuming you're talking about IWDA instead of IWDF?

IWDA and VUSD are two different things. IWDA owns stocks from all over the world while VUSD owns stocks just from the USA (tracking the S&P500).

Despite IWDA being heavy on US, it still lets you diversify further by including other stocks from all over the world. Unless you're really sure that the US will be outpacing the rest of the world in the future, I would say that IWDA is a safer bet, especially if you're only deciding to invest in a single ETF (and not include other stocks/ETFs).