If you are not already using the new Websitebuilder then I think its certainly worth a look to see what the new builder can do. It would depend on what your current website is for, business or pleasure. If its a family, information, fun website and your current website does the job then maybe there is no need to change. But if its business related then we all need to keep up to date with the new style world wide web and search engines, the new websitebuilder does just that ( albeit, its a steep learning curve and nothing like desktop or sitebuilder+) at the end of the day, its your website and I am just offering my thoughts. I am by no means championing the new websitebuilder, BUT I do see the excellent potential. Either way I wish you success with whatever site you decide.
Of course the above still means you would need to add the $2.00/ month extra website. And to try out the different templates on the new builder you need to create a different site for each, BUT you can preview them all using just one new site unlike the current builder you are using. The benefit is that if you were to decide to try the new builder you can do that and your current site would remain up and active just as it is now until such time as you decide you wanted to switch. It is also a responsive builder so you would meet the increasing pressure Google is putting on having responsive sites to do well in searches.