This is a difficult question to answer, because "better" is very subjective - a lot depends on the kind of diving you do (and foresee yourself doing in the future) and what features are most important to you. Like you, I am a new diver and am constantly comparing features of computers while I attempt to make up my mind as to what I really want. For now I have a very basic computer that I acquired second-hand at a very good price that does what I need "at the moment".
For me, the Suunto D5 would be "better" because of the color screen, included AI support (although that involves the additional cost of a transmitter to make use of it) and built-in support in my dive logging software of choice (Subsurface - although apparently you can import the G1 logs into Subsurface with a workaround that you can find here on ScubaBoard, so that might not be a factor for me after all).
On the other hand, for me the G1 would be "better" due to the longer battery duration (only 6-12 dive hours on the D5 according to its manual, the G1 manual states 25 dive hours) and the support for tracking topside activities (excercise, heart rate, etc).
For the kind of diving that I do, the differences between the Suunto "Fused" RGBM 2 algorithm and the Buhlmann ZHL-16C algorithm implemented in the Garmin Descent G1 likely wouldn't be a factor. However, if you are (or plan to be) doing repetive dives with short surface intervals over multiple days, or are prone to rapid ascents (along with a few other factors mentioned in the D5 user guide), then the Garmin Descent G1
may be better for you in terms of the algorithm. I stress
may because the D5 appears to be quite different from its predecessors in this regard - perhaps a D5 owner could help both of us out here.
(SB members reading that comment about the algorithms - please be kind if you post about it. I know it is a contentious topic here - but the OP and I are both new and this is a "Learning Zone"
)
