Its largely down to personal preference, however Fusions are far more efficient.
As an example, I have lvl 20 fusions which produce 44.318 energy with energy 19. They consume 6.727 deut an hour, but support lvl 40 metal mine, lvl 33 crystal and lvl 35 deuterium.
This produces 9.124mil metal, 2.481mil crystal and 2.630mil deuterium a day. The fusion reactor consumes 161.448 deuterium in that day.
(Note on this, these figures are off of a slot 15 planet with a temp of -135 to -95)
if the temp is lower say -168 to -128 (the best I have) The deut production is up to 2.832.504 per day
The cost to build to lvl 20 of fusion is: 143.416.525 Metal, 57.366.604 Crystal and 28.683.198 Deuterium.
The cost to research energy tech to 20 is: 0 Metal, 419.429.600 Crystal and 209.714.800 Deuterium.
In order to produce the same amount of energy you would need lvl 42 Solar Plant (so 22 more fields used)
The cost to build to lvl 42 Solar Plant is: 3.729.823.162 Metal and 1.491.729.808 Crystal
So you can see its actually very cost effective to go fusion when you look long term.
Bear in mind that this illustrates the extreme options, ie an all of the other approach, you can mix solar and fusions of course as well as adding in solar sats as well (although their very vulnerable)
You could for example build solar plant to 16-18 (as mentioned above) then switch to sats or fusion (I advise fusion)