45-man vs. 180-man SNGs

So I initially began taking poker seriously by playing 45-man SNGs on Stars. With a 16.58% ROI at the $1.50 stake over 480 games, I feel like I'm fairly comfortable in this player pool - obviously sample size is an issue, but I'm confident I'm making the correct plays at a given time, and I'm almost certainly not a losing player. I've since moved on to the $2.50 180-man SNGs, where I've generated a whopping ROI of -1.63% over 119 games.

Now, I'm aware sample size is again probably a bit of an issue here. But how likely is it that I'm only break-even in one format and winning in another? Is variance potent enough in the 180 man format that sheer volume is all that you need to overcome it? I ask because neither the player pool nor the gameplay seem particularly different. It just seems like you have to win a few more flips in a row, which in the short term can be the difference between winning $23 and $123, and is something I just haven't managed to achieve yet.

Just asking to see whether anyone with more experience grinding SNGs can shed some light on these games, cheers!