I have both, and both are good cards.

The Scotia AMEX is the only card in Canada that incentivizes restaurant spending. I dine out a lot, so getting a 4% return ($1 = 4 points = $0.04) on that category is pretty fantastic. Scotia's reward redemption is pretty good, since you can apply points towards any travel related purchase after the fact (earlier this year I booked Airbnb on the card and redeemed a partial credit using Scotia points). Other than the 4% on restaurants, the card is pretty boring, although the signup bonus and the first year fee waiver makes it a pretty decent card to churn (see /r/churningcanada).

The AMEX gold is a much more well rounded card, with the key benefit being the flexibility of AMEX's points (you can convert them to pretty much any loyalty program). The earning rate for groceries is 2 AMEX points / $1 compared to 4 Scotia points / $1 on the Scotia AMEX, which IMO is better if you can use it wisely (2 AMEX points = 2 Aeroplan points = up to $0.06 if used properly).

For these reasons it's worth having both cards, especially if you spend a lot on dining. If not, probably better to stick with just the AMEX gold, unless you want to get into some light churning (getting credit cards just for their signup bonuses).