What weight your Rifle; will you be shooting it standing unsupported? Many tactical scopes are on the heavy side and will rather throw the balance of a sporting rifle, or make them unwieldily. Twilight light gathering has as much to do with the glass as the objective so go for the better glass.
We do a lot of poor visibility or dusk shooting in Europe and the European makes like Zeiss and Swaro do show their pedigree in this area. Unless illuminated then the cross hair shouldn't be super fine (Swaro are too fine). Finally, all the bells and whistles like parallax, variable magnification all get in the way of making one good shot count in field at dusk. I do a lot of dusk, lamping and NV shooting. Deer at dusk and rabbit and fox at night. The majority is done with the magnification set a 7x and the rest once set pretty well left alone. If the glass is good there is very little between 42, 50 or 56 in practice other than a wider field of view. I fit what matches the rifle's scale and weight.
Remember for dusk shooting you are shooting at point blank so you just don't need ladder reticles, or even target turrets for the most part.
I've been using a Zeiss Conquest HD5 on my .17 HMR with the Z plex. I like it a lot for the weight, features, reticule and glass. The Zeiss plex is one of the best for field use. Though it has a fixed eye relief through the magnification range it is a bit eye position critical (that can be said for a lot of scopes):
http://i820.photobucket.com/albums/zz128/Muskett_2009/IMG_5153.jpg
I also rate the Zeiss Victories which I have on my .300 WSM Blaser and .308 Milspec. (The Blaser is set up for running boar and the Milspec my culling rifle.) Bar the weight I can't really fault the Victories, though you don't have to go for the fully featured Victories as a less featured model would work as well. I have the Victories because I need the daylight long range ability too. The bit I really like is the 60 reticule. Fast to centre on target the 60 reticule is just superb and though mine have the illuminated reticle I very rarely turn it on. Eye relief and position are really forgiving which only the best hunting scopes have (Jap and American scopes rarely have this important feature; why European scopes are so good in the hunting field. At night or for running game it makes a huge difference as does rifle fit). Money no object the Zeiss Victories are my recommendation, but you could go for a more basic model:
http://i820.photobucket.com/albums/zz128/Muskett_2009/IMG_4924.jpg
That lamp has been changed to a modern LED Dereelight.