Is it best SATA II or SATA III SSD FOR - Dell Optiplex 3020 SFF

Please assist with this:   // I want buy on Amazon Prime day[10-11 July] – so reply asap…

Samsung 850 EVO 250 GB 2.5 inch Solid State Drive - Black

https://www.amazon.co.uk/gp/product/B00P736UEU/ref=ox_sc_act_title_1?smid=A35TJMBOJMSUPU&psc=1  

Samsung 850 EVO 250GB 2.5-Inch SATA III Internal SSD (MZ-75E250B/AM)

https://www.amazon.com/Samsung-2-5-Inch-Internal-MZ-75E250B-AM/dp/B00OAJ412U/ref=sr_1_1?s=pc&ie=UTF8&qid=1499513483&sr=1-1&keywords=SSD&refinements=p_n_feature_keywords_four_browse-bin%3A6158693011%2Cp_n_feature_three_browse-bin%3A14027458011%2Cp_n_shipping_option-bin%3A3242350011   

these two SSDs are the same? Or the first is SATA II and second SATA III ?

For this desktop PC – what is best to buy… from above?

Dell Optiplex 3020 SFF Intel Core i5-4570 3.3GHz 8GB RAM 500GB HDD Win 7 Pro AMD Graphics - 2013-2014 model  

Is it best SATA II or SATA III SSD for this PC ^^^ ???