Honest take
Wellfit Marina has the broader class schedule. Shams Community Gym JBR has pool access — Wellfit Marina doesn't. They sit in different tiers — Shams Community Gym JBR is mid, Wellfit Marina is premium — so they suit different budgets.
Pick Shams Community Gym JBR if walking distance from shams 4 residences.
Pick Wellfit Marina if 35.
Affiliate disclosure: The "Visit" links above are affiliate links where partnerships exist. Pricing and listings are based on real research, not commission rate.