First let me say I have a bias for Archistories products, I have built them all and they are well designed buildings loaded with detail and historically accurate. I have a bit of a face-off between Archistories ARC-112121 Roundhouse in one corner and Marklin recently released 89982  which includes the turntable with 5 pole motor, transformer, turntable control, 2 building kits in the other corner plus you get 6 block sections of track . There is no knock out punch here which one you choose is personal preference, but I would like to point out some interesting reasons and options that might sway a choice toward Archistories. Archistories Roundhouse ARC-112121 is expandable with ARC-113121 Roundhouse Stalls: before you finish the building of ARC-112121 you add stalls in pairs. The Marklin set is a 6 stall roundhouse, they have not released an accessories building kit to expand the original roundhouse. 4,6,8,12,18 stalls the roundhouse prototype in Europe and the United States came in all sizes so choosing the Marklin could be a good choice if you want to model a more modern roundhouse versus the earlier Prussian roundhouse offered by Archistories. If you choose the Archistories Roundhouse here is a solution to add a turntable: Marklin offers a 5 pole motor upgrade for the early turntable 8998, that motor goes by part number 211914. Walthers currently has this in stock for retail $49.99, Trainz on Ebay is also selling them for the same price. Ordering through your local dealer might save you some money. The motor upgrade is easy to do, I will be following up with a step-by-step for this in the next week.

Price comparison:

Archistories Roundhouse with 6 stalls and Marklin Turntable w/5 pole motor: Archistories ARC-112121 + ARC-113121= $113.52, used/new vintage Marklin 8998 turntable= $150 (average Ebay price), and Marklin 211914 5-pole motor for $49.99= $313.51

Marklin 89982 is listed at Walters  for $549MSRP- retail train shops are selling for the discounted price of $449. This option includes 6 block sections of track, transformer and an additional building feature.

I made the choice for option 1 Archistories because I like the architecture of the roundhouse better.