TI will be darker in color but lighter in weight and has a physical warmer feel and aesthetically more serious look due to the brushed finish. The stainless model will be brighter and pop more partly just because stainless is a lighter colored metal and partly because of all the polishing. Generally, I think the FF is under strapped, I wish it had a 24mm lug width tapering to 22mm and a stiffer strap to manage the heavy watch, titanium is a big win here for wearability. The 1315 movement is really nicely done too, something worth seeing and I think the stainless case back is a travesty in that regard since the movements no longer need the antimagnetic iron covering.