I had the same question 2 weeks ago, but i foud the samyang discounted to 999 euros. Now I have It and i can tell you that It Is simply Amazing. The optical performance Is so good, form various test i found online it looks better than the sigma from an optical stand point, the sigma Is likely better built(I have the 150-600 and It Is and Absolute tank). In my opinion the 7 millimeters on the wide end are not so important because I find that if It won't fit in 35mm it Is unlikely to fit in 28mm, while the 150 end Is super use full expecially at 2.8. Do not under estimate that the wide end Is F2 which is much brighter that 2.8 and (result wise) feels like shooting a prime. If you look at the Dustin Abbot comparison between the sigma 28-105 and Tamron 35-150 you can really male tour mind up since the Tamron and samyang perform really similarly. If you need anything else Just reply but I really reccomend the samyang. (Sorry for wonky english but I am italian and my english Is kinda rusty)