You have not explained what you plan to do with your grapple or how much you intend to use it. What type of land and how much land. In general I would only buy a dual lid grapple based on the reasoning that the grapple will adjust to the load you are carrying much more than a single lid model, this may not be so important for moving brush but if you are going to be moving tree trunks and various hard objects the dual lid does a much better job of grasping the load better where there is differences in sizes of material on each side of the grapple.
The other key question is what style of grapple, as you have observed there are a lot of different products out in the market place from a lot of different manufacturers / resellers. A lot of the market and marketing is aimed at the strength v's weight, Everything Attachments sells very nice lighter weight strong product, they have a long waiting list and are not cheap, with your MX you do not have to fall into the grapple weight issue that impacts the smaller B & L series. You MX loader will run just about any 60" - 66" grapple on the market and still leave you well over 1,000lb of lift capacity . I recommend you load your rear tires and use either a ballast box or rear implement of at least 700lbs when using your grapple.
Another big question on grapples is what are your expectations for ground engagement, are you planning to dig or up-route stumps? Personally I don't believe that a grapple should be used for heavy ground engagement. There is a lot of difference in scrapping 4" into the ground to remove brush v's fighting a 16" stump. Most steel on the tines is 3/8" thick, I don't care who makes the grapple or what grade of steel it is you will bend it with your MX if you are too rough with it. The HP ratings are a real rough guide don't place too much importance on them as long as the grapple is roughly in your HP range.
Grapple pricing is very wide in the market, pricing has increased a lot in the last year, equipment availability at times is difficult. I own several grapples that I use across L / MX and track loader equipment. I have always looked more at the value side of purchasing a grapple, I'm not sure that an expensive model is really any better than a mid priced model. The only exception to this is the weight / strength issue of smaller tractors with limited loader capacity.
If I was in the market today buying a new grapple for my MX I would buy a MTL RG-7 HD Root Grapple in 60" width from MTL Attachments. They are currently in stock and price including shipping is $1,699. I own one of their smaller grapples and think they are amazing value. All piviot points have grease nipples, cylinders have guard covers and weight is average at 530lbs. You are going to find many grapples that are in the $2,700 - $3,700 range, my opinion is they are not worth the increased cost.
If you are really into ground engagement / stump removal I would recommend that you take the money you saved on the grapple I recommended and buy a Titan HD stump bucket, at 500lbs this thing works well on the front of an MX other than it is a long way forward and visability is not great but it sure digs well!
Good luck in making your grapple selection, no matter what you buy you will find it an amazingly useful attachment.
I also add about 1K of ballast and have loaded rear tires. My 3rd function was installed by dealer at no labor cost. Easy to add with rear tires removed and seat removed.