I have to disagree with Eddie on this one. I have pulled well over 100 3 axle trailers. Very common in the boating industry. I have never had a tire issue. Actually the tires to me are a advantage. They are cheaper and a more common size so finding them when you have a flat or blow out on a trip is much easier. You also have 50% more brakes. To some this is a negative but not to me. I would rather have 50% more brakes and bearings to maintain because the advantages outweigh the disadvantages.
The other factor is load height. I have had the same boat on a 2 axle trailer with 5,200# axles and on the same trailer but with 3 3,500# axles. The load set 6" lower which makes it that much easier to tow, get under bridges, under barn doors, ect. Not only do the tires size lower the load but also the springs on a 3,500 vs a 5,200 are about 4" lower so along with the 2" less tire height you get the advantage.
The load height will also be a advantage on a flat deck/equipment trailer like you are looking at. The ramp angle will also be less for easier loading. To me its a no brainer, buy this trailer if its what you want and need.
Yes, I see some tire flex but I have never had a tire issue because of it. I would take a 5 axle trailer over a dual tandem like I used to have on my 30' GN 25,000# GVWR trailer. Talk about a pain.
Chris