I think the deck material will be the same thickness and the 6mm vs .250 is simply conversion rounding.
Take a look at this thread for more information:
http://www.tractorbynet.com/forums/...rge-flail-mowers-post4480299.html#post4480299
The posting by Jack Yuan is interesting and you can perhaps PM him with questions since he sources the mower for Victory. Perhaps he also knows who sources Value-leader.
Jack also commented in this thread when I mentioned my AG180 mower in this post:
http://www.tractorbynet.com/forums/...alk-flail-mowers-post4514172.html#post4514172
The comments are for the AG1xx series mowers but likely relevant for other series.
If you search for AG180 flail mowers you will find several outfits selling similar mowers including Europe, New Zealand and Australia. You can likely do the same for the model you are considering and compare various suppliers' features with Victory and Value-Leader brands.
I bought a no-name AG180 from a local supplier who imports them in my area. I think the build quality is good. The welds are continuous and look good (to my untrained eye) and the overall finish looks good.
Jack did highlight valid differences for my mower though. In order of importance for my application they are:
1.rotor quality and balance: vibration and balance weights--my mower has virtually zero vibration with 292 g and 257 g weights on each end. That does not seem excessive since just the bolt for each of the 16 blades weighs 225 g and the blades average around 1,040 g.
2. vent plug instead of solid plug on horizontal shaft from the transmission to belt pulleys. Mine had a solid plug which I replaced with a vented plug. I also let my vendor know Jack's recommendation.
3. transmission: mine has a smaller 50 hp rated transmission than Value-leader's 65 hp rating. Jack said some vendors make their own. Since my tractor is just 28 hp at the PTO I am not too worried. Also, my manufacturer supplied the transmissions for Comer in Italy and I believe they have a good reputation for driveline parts.
4. flail blade weight variance. Jack supplies forged vs cast blades for more consistent weight. But he did not specify an acceptable variance. The weight range for my existing 36 blades (2 sets of 16 plus 4 spares) was 1,003 to 1,072 g. I think it is easy to compensate by grinding sets to similar weights (I did my spare set yesterday). I also compensated for weight difference in my current set (which I have not ground to similar weights) by installing them in balanced pairs as shown in this post:
http://www.tractorbynet.com/forums/...alk-flail-mowers-post4559547.html#post4559547
I don't know if it is worth the trouble, but it can't hurt.
5. front debris guard: my mower uses hanging chains vs steel plates which are safer.
6. BX (segmented) instead of B (solid) V-belts: Jack Yuen mentioned this in another post. BX belts create less heat. I assume the Victory mowers use BX belts since he sources the mowers. I think most flail suppliers use B belts.
One "plus" for my mower is an extra cover protecting the lower part of the standard fan belt guard. It may have saved my standard guard a couple of times.
Jack's comments are good in helping evaluate mowers. Of course there are things such as bearings that we cannot see, and availability of parts is important.
Good luck in your search.