Yes!... there is a best! — a comparison

Compare FrameSpace and EconoSpace to Arlo Spacemaker, Buckwalter Innerspace and Preservations Space 1. See the reasons why FrameSpace and EconoSpace are the better choice in picture frame spacers.
  FrameSpace EconoSpace Spacemaker Innerspace Preservation Space 1
 
Spacemaker
(Arlo)
Innerspace
(Buckwalter)
Preservation Space 1
U.M.S.C.O.
Permanence
Mechanically
Permanent
Relies*
On Adhesive
Relies*
On Adhesive
Relies*
On Adhesive
Relies*
On Adhesive
Shear (Sag) Resistance **
Mechanically
Permanent
41 lbs.**
34 lbs.**
27 lbs.**
13 lbs.**
Approximate
sag weight per 100 feet of 1/8"
N/A
Mechanically
Permanent
9 Oz. Hollow for lightness and stiffness
17 Oz. Solid
17 Oz. Solid
9 Oz. Hollow
Removable?
Easily &
Repeatably
No
No
No
No
Adhesive
Thickness
None Required
.005 In (5mil)
.002 In (2mil)
.002 In (2mil)
.002 In (2mil)
Sizes
Available
(Airspace)
1/8, 3/16, 1/4, 3/8, 1/2, 3/4 & 1/4 Dbl
1/16, 1/8, 1/4 & 3/8
1/8 & 1/4
1/8 & 1/4
1/16, 1/8, 1/4
Length
Full 60"
Full 60"
58"
59"
48"
Colors
Available
Most Available in Clr, Blk, & Wht Paintable
Clear, Black & White
Clear, Black,
& Smoke
Clear & Black,
Clear & Black
Special
"Allowance"
required?
Standard 1/8"
1/32 - 1/16"
recommended
?***
?***
?***
Finish
Glossy
One side matte,
other gloss
Glossy
Glossy
Glossy
Keeps glass from shaving off bits of wood, paint, & leaf in wood frames. Reduces glass chipping in metal rames.
Yes
No
No
No
No
*
 Pressure sensative adhesives will not stick permanently to unfinished wood as the resins will adversly affect the adhesive. The adhesive must be adhered to the glazing for permanence.
**
 Manufacturers note: No pressure sensitive adhesives are permanent. Temperature, humidity, and the persistance of gravity will eventually overcome bond. The adhesive used on Econospace is much thicker and stronger than the others and because Econospace is lighter, it will work fine for smaller frames. Test results are from an independant lab comparison test using 3" of engagement on glass. Test report available upon request.
***
 No instructions included in package. Spacer will move with the glazing the amount of the allowance and possibly move spacer into view. If spacer is used with 1/8" allowance and engaged half on - half off glazing to "center" the glazing, this reduces adhesive engagement and thereby reduces bond strength and longevity.
Both Framespace and Econospace meet FACTS Standard for Maximum Preservation Framing