Do different needle types make a difference to tension?
How I did it:
Cast on 36 stitches and knit 3 border stitches either side and 30 rows stocking stitch,4 rows garter stitch top and bottom borders
Tension measured over the 30 sts x 30 rows and compared prewash then post wash.
Measurements are done in metric to obtain the very small differences in measurements. All swatches were treated exactly the same way, washed post knitting together, dried flat.
The needles are all marked either 4mm ,US 6 or English old size 8
Needles are:
White plastic 4mm straights
Grey metal 8 straights ( old needles marked in English size pre decimal sizing)
Tortoiseshell 4mm ( I think these are probably plastic as real tortoiseshell would not have been marked in metric sizing here)
Signature stiletto points fixed circular needles, US size 6 but marked at 4mm. I have always felt these to be a little finer than a true metric equivalent.
Addi rockets, metal 4mm (fixed circular)
Knitpicks interchangeable harmony (wood) needles.size 6 US
Glass needles US 6 (fixed circular)
Karbonz 4mm (interchangeable circular)
Cubics 4mm (square wood interchangeable circular)
Circular swatch I used Signatures
The Results:
white plastic straights
Used 11g
Prewash 133mm x 93 mm
Post 140 x 90 cm
Pre wash tension over 10 cm = 22.5 sts x 30.6 rows
Post wash tension = 21.4 sts x 33.3 rows

metal straights
Used10 g
Prewash 131mm x 98 mm
Post 140 x 90mm
Prewash tension over 10 cm = 22.9 sts x 30.6 rows
post wash = 21.4sts x 33.3 rows

tortoise shell
Used11g
Prewash 128mm x 101 mm
Post 140 mm x 90 mm
Prewash tension over 10 cm = 23.4 sts x 29.7rows
Post wash =21.5 sts x 29.7 rows

Addi Rocket
Used 11g
Prewash 136mm x 97mm
Post 140 mm x 9.9 mm
Prewash tension over 10cm =22 sts x 30.9 rows
Post wash = 21.5 sts x 29.7 rows

Knit picks harmony
Used 11g
Prewash 128mm x 101mm
Post 140mm x 99 mm
Prewash tension over 10 cm =23.4 sts x 29.7 rows
Post wash = 21.4 sts x 30.3 rows

Signatures
Used 10g
Prewash 132mm x 94mm
Post 142 mm x 90mm
Prewash tension over 10cm = 22.7 sts x 31.9 rows
Post =21.1 sts x 33.3 rows

Glass
Used 11g
Prewash 130mm x 93mm
Post 138mm x 92 mm
Prewash tension over 10 cm = 23 sts x 32.2 rows
Post =21.7 sts x 32.6 rows

Karbonz
Used 11g
Prewash 130mm x 100mm
Post 140mm x 92 mm
Prewash tension over 10cm = 23 sts x 30 rows
Post =21.4 sts x 32.6 rows

Cubics
Used10g
Prewash 132mm x 93mm
Post 137mm x 92mm
Prewash tension over 10cm = 22.7 sts x 32.2 rows
Post = 21.8 sts x 32.6 rows

Circular swatch done on 4mm Signatures
Used 13g (extra yarn because of stranding across back to knit in circle)
Prewash 131mm x 98 mm
Post 142mm x 92mm
Prewash tension over 10 cm = 22.9 sts 30.6 rows
Post = 21.1 sts x 32.6 rows

The results:
(rounded)
Signatures gave the least number of stitches per 10cm in both the flat knit & the circular piece at 21 stitches
The glass & cubics gave the most number of stitches per 10cm at 22 stitches
All the straight needles and the Signatures gave the greatest number of rows over 10 cm at 33 rows
Addi Rockets gave the least at 30 rows

It would appear that there is very little difference, 1 stitch or less, over the 10 swatches I knitted in stitches per 10 cm, even when knitting in the round.
The bigger difference is seen in the rows per 10cm 30 to 33 rows.
Note: for those not familiar with ColourMart yarns- these yarns tend to ‘bloom’ after a wash so hence the differences pre/post wash.
10cm=4”