I know "you can't go wrong with either one" but I'd still like a few comments.
You can't know how much I agree with this comment. For the past seven years, I've been supporting the 3D habit of my young son and I, and considering the number of planes and components I've bought, nothing is less helpful than someone tell me "you can't go wrong with either one" or "just buy it and fly it".
This explanation is probably more than you bargained for, and asking guys which one they like better is something I do also as long as I see a video of them flying the plane to get a feel for what they want out of it. If they don't do much, then they don't expect much, and if I flew around in the pattern, I'd probably put a lot less effort into it.
Anyway, to eliminate disappointment, and along with what I know about aircraft design, I assembled the physical characteristics that I like in a plane, and now rank planes accordingly. Most of it, of course, is subjective, and others will like higher or lower values, but I've found that the planes I have the most fun with have the following profile.
- A wing loading under 30, but unlike cube loading, wing loading is tough to keep down as the size of the plane icreases, so with a wingspan over 100 inches, you have to compensate.
- A wing cube loading in the 8.0 to 8.5 oz/cu ft range, but some XA and IMAC guys find this too light on the wing and will prefer something no less than 9.5. I've seen some really good IMAC performers come in at 10.5. I still prefer something under 8.5 or 8.6.
- A power loading of 250 Watts per pound or higher, and I really like 275+ W/lb better. Some will say that's 'overpowered' but I'm not sure what that means. As far as I'm concerned, give me the power and I'll figure out how to use the throttle.
- A 1.7-to-1 thrust to weight ratio, and 2 to 1 is just super, IMO. Again, some will say this is wasted power, but if you get low and slow and out of position, you'll wish you had it.
- An aileron to wing area ratio of greater than 26%, and many are coming in at 32% now so this has become less of a priority.
- An aspect ratio that depends on the fuse-to-wingspan ratio. This is also low on my list, but planes that have nearly the same fuse length and wing span will need a lower AR than more scale planes. My older aerobatic planes have an 88% to 90% fuse to wingspan, so an AR up to 6 is fine, while most of my current planes are almost 100% with the spinners on, at which point I like to see a number just under 5.
I've used this now for a while and it has never disappointed me. Of course, a lot of this means watching the all-up weight of the plane, and how it is powered.
With that said, the MXS and the 74 Laser have an interesting story.
With a 12.8 lb AUW with a piped DA-35 spinning a 20B Vess to 7650 RPMs, the Laser will have a 25 wing loading, an 8.85 cube loading, a 274 W/lb power loading equivalent, and a 1.91 to 1 thrust to weight ratio. The AR is 4.76 and the aileron ratio is 30%. Very good numbers in my book. I know the power is possible, and the AUW may need to be monitored during the build.
As a comparison, other planes with similar numbers are the 71" AJ Slick at 10.35 lbs with 2880W, the EF 78" Extra 300 at 12.64 lbs with 3000W, the 3DHS 72" Extra 330 at 10 lbs even with 2400W, the 91" Aeroworks Extra 300 Freestyle at 5400W, and a few more with a slightly higher and a few more with a slightly lower PAR.
It is my understanding that the MXS with the same DA-35 with an ES pipe can come in around 13.6 pounds if you control the weight during the build. If this is the case, then the WL will be 24, the cube loading will be 8.0 (both because of the increased wing area), a slightly lower 250 W/lb power loading, and a slightly lower 1.76 to 1 thrust to weight ratio. The aspect ratio and aileron ratio is about the same, just slightly different because of the wingtips.
The increased weight and surface area will also increase the parasitic drag of the plane, which means a slower acceleration and possibly a slower response to control input.
We also have to consider that perhaps because of the lower power loading numbers, many guys are using the DA-50 and the 50cc motors, like the Motrolfly DM5335-195, which will add weight and increase the power. If you can keep the plane under 15 pounds (all-up), the only real change is that the wing loading and cube loading will increase a bit to about 27 oz/sq ft, and 9.2 oz/cu ft. Although the wing loading is fine for me, this is a bit of a noticeable difference for me since I prefer 8.5 oz/cu ft.
Buy it, Fly it.. You cant go wrong.. LOL