New bike size comparisons

[DaveyA]

Hello fellas
I am looking to buy a new bike. I used their bike sizing guide (Merida) and it came up with a medium as recommended size. Compared to the bikes I have now it appears to be bigger than I expected. I'll list the various sizes and differences. I have looked for so long that I am more confused.
Current bike(s) all around these sizes give or take.
Cube c62 small frame.
ST 46.4
TT 53.7
Head tube 124
Reach 386
Stack 544

Merida Scultura E bike. Recommended size M
ST 51
TT 55.5
HT 175
R 395
S 597

Merida Small
S 49
TT 54
HT 175
R 384
S 581

I have calculated the differences between the small and medium Meridas compared to the Cube and am still unsure which would suit best. The Merida have much taller head tube, I am wondering whether it would compensate for the longer top tube. I would prefer a more upright position as I have a slight back problem but don't want to feel cramped on too small a frame. Here are the size differences.

Cube > Merida. Medium frame. ST 4.5 cms longer (than Cube). TT 1.5 cms longer. Rch 9mm longer St 33mm taller.

Small frame ST 2.5 cms longer. TT 0 .3mm Rch 2mm longer St 37mm taller.

I know wisdom dictates to always go smaller but I would greatly appreciate some thoughts and advice before I take the plunge.
Many thanks in advance.

 

[T4tomo]

reach and stack are key measurements.

if your cube feels right reach go with the small Merida.

Teh stack is as you say higher on teh merida as it has a taller ead tube, the will result in a more upright position, but if you cant reach you cant reach .

that said, reach difference of 10mm isn't much, just one increment up or down on stem length.

 

[DaveyA]

Thanks for your input.
I have gone with the small size. It seems closer to my current bike size.