I have noticed that using Html.Partial performs slowly in Sitefinity.
I changed a dynamic icon I use frequently to a partial and use Html.Partial to render it. Doing this drastically slowed down the page's load time on my production server. Every partial rendered took an extra .3s to load. Since I had the icon on the page 42 times, it took about 13s for the page to load.
The performance is so bad that I have to now think about every partial I use and whether an extra .3s load time is worth 1 use of the partial.