SPSite site = properties.Web.Site in event receiver

I have an event receiver and would like to ask what is the best method and why.

1.

using(SPSite site = new SPSite(properties.SiteId)
{
    using(SPWeb web = site.OpenWeb())
    {
       //code
    } 
}

OR

SPSite site = properties.Web.Site;
SPWeb web = site.OpenWeb();

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