if you had to choose between a Dual Recto or 6505+, what would it be?

That is normal. The "Modern" setting is always a touch louder. The presence knob for distortions on the 3 channels only has a usefull range from 6-12 o'clock, past halfway and its just fizz, on the 2 channel models its pretty useful across its entire range of motion. FWIW I have found the most consistently recordable settings with my 3 channel to be on channel 2 "Vintage" mode, silicone diodes, ss rectifier, boosted with a Boss Sd-1, MXR Badass OD, or a Digitech Bad Monkey oddly enough. The "Modern" setting even sounds a bit more controlled on channel 2 than 3 for whatever reason.
 
beware the 5150 has massive loose low end as well, if you dial it wrong of course.
In the end 5150 more mids, mesa no mids at all.
If you boost mids on the mesa, the amp won't sound better, just weird... it seems it boosts the wrong frequency lol
It's not made to be an amp with mids cranked, it wasn't conceived for that, it was just to be brooooootal ahhaa
I own both and I love them
 
Well, here's a short little test of 5150 vs Dual Recto through a Marshall Lead 1936 2x12" cab.

https://dl.dropboxusercontent.com/u/6443251/Turkey Massacre 5150 vs Recto Test.mp3

Guitars only: https://dl.dropboxusercontent.com/u/6443251/Turkey Massacre 5150 vs Recto Test guitars only.mp3

Not totally proper of a test as mic placement was moved and I didn't exactly dial the amps in to sound as close as possible, more what sounded good in the room and through the mic.

Drums are Metal Machine and I grabbed one of the MIDI grooves that was included in the pack just to jam to.

Let me know what you think of the tones and also the mix itself. Playing isn't anything perfect, so apologies for that aspect of it.
 
Both amps are good but the rectifier definitely doesn't deserve to be that expensive compared to the 6505.
With the same money you can buy a 6505 and a Mesa Cab which are fantastic.For me, rectifier is totally dependable on a good boost, while the 6505 can work with out too.Also the 6505 works great with the marshall cabs that you find everywhere, while the rectifier doesnt for me.Of course the rectifier has better cleans, but you probably aim for the distortion.