I think i would probably take this both are extremely rare but the ultima could be faster (depending on what engine it has) this does have the advantage of not having to build it yourself and all but lets ignore that and go by preformance style and design personally i think this wins in style and design but i'm not sure about preformance
Re: This vs Ultima GTR well, I'd say this wins the style- and, if one can associate ti with a car such as this- practicality- it might actually have a trunk. But any Ultima I dare have would be much faster than this- depending on what fits-an old bmw v12, a new merc v8 supered, a ford v12 (aston Martin), or, if it fit, the Viper v10-add titanium and carbonfiber to strengthen the chassis even more, tweak the suspension, and the ultima would dis this any day