One will be higher and one will be lower (perhaps they're both the same). Check the product data sheets to be sure of the values. Personally, I wouldn't bother with a 10w-30 in synthetic, particularly a HM synthetic.
Mobil 1 5w-30 HM and 10w-30 HM have different approvals. The 5w-30 is ACEA A1/B1 and A5/B5 and 3.3 HTHS, and the 10w-30 is A3/B3 and 3.5 HTHS. I bought some of the 10w-30 when we had a Saab 9-5 which wanted A3/B3. The Saab is gone, but I still have some of the oil.
HTHS viscosity is best thought of as how thick an oil is in the bearings of an operating engine. The HTHSV spec' is given at 150C but it's usefulness applies at normal operating temp's when comparing different oil viscosities.
All engines require a minimum HTHSV under maximum load which typically is in the 2.6cP-3.5cP range but that doesn't mean you need to run a oil with that rating if you're not seeing high oil temp's, which is a common misconception.
A typical 0W/5W-20 oil has a HTHSV rating of 2.6cP but it's HTHSV at 100C will be in the 5-6cP range. That's why engines spec'd for 30, 40, 50 or even 60 grade oil will run very well on a 2.6cP HTHSV 20 grade if the maximum oil temp's are sufficiently contained.
So as has been pointed out, an oil with a higher HTHSV rating is not better, it's just a heavier oil. If you want to know what the best HTHSV is for your engine and most importantly the way you operate it, that will take some info gathering including max' oil temp's and minimum oil pressure.
Or if you're not into that (any very few on this forum are) just run the lightest oil (lowest HTHSV rating) recommended by the engine manufacturer. They have already figured out how heavy an oil is necessary including the most extreme use at maximum oil temp's.