I have a 28' (23+5). I think I'd go longer then 30 if you want to put them both on there and have some room left. If you wanted to carry extra attachments you'd either be good at tetris to make them fit somewhere on the deck, or have a deck up on the neck to set a few things on. Also if you plan to have 16-20k on the deck plus the trailer weight (figure all of 7,000lbs for a quality trailer) I'd get 12k axles and electric over hydraulic brakes. Electric drums suck, poor excuse for brakes. I hate mine.
My 23+5. 10.5' snow box, 7.5' plow standing up right, 72" grapple bucket, 78" dirt bucket up on the neck, and the TL230 and 48" pallet forks on the rear. I think the only thing missing was my bale spears and boom lift, couldn't figure out where to put them safely so they went on another trip.
Same trailer again. 1941 JD "A", Case 445 and 80" bucket, atv on the ramps.
Same 23+5. The 10.5' snow box and my TL230.
Here's the farm's 30+5. Case 90XT and SR270 with rock buckets and then a grapple bucket right up against the front.
Edit. I plan to go with at least a 35ft on my next trailer. 36-40ft is more likely. Hydraulic dove (lets you use all the deck space with equipment instead of loosing the last 4-6' due to ramps, 15k axles with EOH drums, 17.5" tires (with polished Alcoa's of course) extra storage boxes, extra lights, 2 speed jacks, and a winch plate. Costly, but big enough you could still load multiple pieces of equipment on it and still be ok instead of 10-15,000lbs over weight and having zero deck space left.