Glad you added the disclaimer, it was starting to sound pretty biased.
Disclaimer - I WAS sponsored by B70, am no longer (yeah, you guys heard right, free-agent baby, who wants a MOP Age Grouper??)
I have used both.
I loved the Helix. Never chaffed, always flexible. But I had to get a new one every year for lots of micro-cuts and dings that would lead to major holes or tears.
The Huub Archimedes 3:5 is a super flexible suit with a great stabilizer. The suit really puts you in a great position, especially if you are not a very effecient kicker. I just didn’t like the bulk of materials at the back of my neck and it caused chaffing. But maybe that was just me and it won’t happen to anyone else. However, the claim that it is more durable than the Helix is VERY questionable. The suit is super supple. It feels like butter. But it is also “thin skinned” and must be handled delicately.
Delicately - By that I mean that you can’t just grab the suit and yank it on and then grab some rubber and yank it up some more with force. You can’t grab it by the neck line and yank on it to hike it up some more. You can’t throw it on the ground in transition (if it’s asphalt) and kick it to the side and expect it to be ok. I don’t mean you need to lather up with baby oil and 5mil thick rubber gloves, but you do have to use caution.
Both the Helix and the Huub are similiar in type of care needed.
That being said, the Helix is for swimmers. I mean real swimmers laying down almost pro times and have an effective kick and excellent body position. It’s my opinion that the Huub Archimedes 3:5 is more for FOP triathletes that don’t kick as much and need a little bit of help with their body position. I would think the Huub Archimedes 4:4 is more for the MOP triathlete that needs help keeping a better body position.
Now, to answer the questions:
Fit to sizing chart? - B70 Helix is true to size chart, err on the side of smaller. The Huub runs bigger than exected because of the amount of stretch in the material. Go one smaller than you would think.
Flexibility? - Both extremely flexible. I would likely give the nod to Huub for this.
Feel in the water? - THe Helix gives the swimmer a lot of feel for the water as the inside of the arms are paper thin. The fabric is the same as their skin suit I think. Huub is thicker, which has other advantages, like forciing a high elbow or else your arms will get tired and sore.
Quite honestly, they are both fantastic suits. I think the B70 Helix has been the benchmark for a long time, but Huub has been making some fantastic technological advances.
Good luck, either suit is great.