I've used a few different chestrigs in my time.
In the '90's I started out with a 42 Pattern Arktis rig. 3 triple 5.56 magpouches in the middle (Also fit 2 x 7.62 G3 mags) and two GP pouches, one on each side, a map pocket behind.
I strapped my radio on next to the GP pouch and a compass pouch for compass and a multitool on one of the shoulder straps. A very basic chestrig design, but very useable. Only negative was the X straps around my back, that chaffed my neck by end of a week.
The 42 Pattern Chestrig was used during vehicle borne scout missions. If I was dismounted for extended periods, I wore a daypack as well.
I still have that chestrig in my locker for old times sake, bombproof construction.
Went away from chestrigs for a while, using beltgear and combatvest setups in an infantry role.
By '03 when we went to Iraq I got a Blackhawk STRIKE chestrig with a front plate pocket. At that time we didnt wear our armor at all times, but had it with us in the vehicles. So I chose to run one of my plates from my vest in the platecarrier when out and about. Pretty similar setup to my 42 pattern rig. The STRIKE rig allowed for a H pattern of the straps, which was more comfortable than the X and kept it away from my neck.
I also played around with a combatvest and a HSGI Wasatch platecarrier/chestrig during that deployment.
After I left the Army in late '04 and began contracting in Iraq, I used a Diamondback Tactical Low Vis rig for a while. It also had the X straps, but since they were thin and not wide like the Arktis rig, they didnt chafe the neck as much. Great for low pro missions with low pro armor and a shirt on top. I wish, I still had that rig, if nothing else, than for nostalgic reasons.
I then went to a full Paraclete RAV setup, then a Paraclete HPC setup for most of my time.
Later on, I got a Eagle Poul Howe UCR rig, which I didnt use as much since it had thick X straps that bothered me, oh well.
Eventually around '11, I got a Gen 1 Mayflower LPAC armor set with a clip on molle panel, that I set up with pouches to fit my mission and found that, this was the best way to carry a chestrig, clipped onto my armor and detachable if I needed armor, but no fighting gear, but fast to clip on if needed. In my humble opinion, Mayflower makes the best chestrig setups in the business.
H straps are more comfortable than X straps, but clip on chestrigs to armor are the best option. Less straps that go around your neck and weight savings on top of that.