Is the Casio F-91W better than the Seiko Prospex "Turtle"?

Neither is objectively better — they serve different preferences. The Casio F-91W (~$20) offers Quartz Module 593 with 7-Year Battery power reserve, while the Seiko Prospex "Turtle" (~$500) features Automatic Caliber 4R36 with 200m (20 ATM) Diver water resistance. Choose based on your priorities: Casio (Japan) craftsmanship vs Made in Japan engineering.

Casio F-91W vs Seiko Prospex "Turtle" — which is better value?

The Casio F-91W offers better upfront value at $480 less. However, the Seiko Prospex "Turtle" may justify its premium with superior finishing, heritage, or resale value.

Can you wear the Casio F-91W and Seiko Prospex "Turtle" daily?

Both are suitable for daily wear. The F-91W at 35mm with 30m (Splash Resistant) water resistance handles everyday situations. The Prospex "Turtle" at 45mm with 200m (20 ATM) Diver is similarly capable. Both feature Acrylic for scratch resistance.

Head-to-Head Comparison

Casio F-91W vs Seiko Prospex "Turtle"

Name: Casio F-91W
Brand: Casio

Casio's timepiece meets Seiko's diver

Quick Verdict

The Casio F-91W (~$20) offers Casio Digital Quartz (Battery) precision at $480 less than the Seiko Prospex "Turtle" (~$500). The Prospex "Turtle" counters with Made in Japan craftsmanship and 200m (20 ATM) Diver water resistance. Both are exceptional watches for their respective price points.

Transparency — We earn a small commission on purchases made through our Amazon links. This doesn't affect our editorial independence.

Casio

F-91W

~$20

Check Price Full Review

Seiko

Prospex "Turtle"

~$500

Check Price Full Review

Specifications Compared

Feature	Casio F-91W	Seiko Prospex "Turtle"
Price	~$20	~$500
Case Size	35mm	45mm
Movement	Quartz Module 593	Automatic Caliber 4R36
Caliber Type	Casio Digital Quartz (Battery)	In-House Automatic Manufacture
Power Reserve	7-Year Battery	41 Hours
Water Resistance	30m (Splash Resistant)	200m (20 ATM) Diver
Crystal	Acrylic	Sapphire Crystal
Case Material	Resin	Stainless Steel
Origin	Casio (Japan)	Made in Japan

Category-by-Category Analysis

🎨

Design & Aesthetics

Edge: Draw

Casio's design language vs Seiko's approach

⚙️

Movement & Performance

Edge: Seiko

Quartz Module 593 vs Automatic Caliber 4R36

📏

Wearability & Fit

Edge: Casio

35mm vs 45mm — different wrist presence

💰

Value & Cost of Ownership

Edge: Casio

Casio is $480 more affordable

💧

Water Resistance

Edge: Seiko

30m (Splash Resistant) vs 200m (20 ATM) Diver

Our Verdict

Casio

F-91W

Choose the Casio F-91W if you prioritize Casio Digital Quartz (Battery) engineering, Casio (Japan) craftsmanship, and 30m (Splash Resistant) water resistance. At ~$20, it delivers Quartz Module 593 with 7-Year Battery power reserve.

Check Price on Amazon

Seiko

Prospex "Turtle"

Choose the Seiko Prospex "Turtle" if you value In-House Automatic Manufacture technology, Made in Japan heritage, and 45mm proportions. At ~$500, the Automatic Caliber 4R36 with 41 Hours power reserve makes it a compelling choice.

Check Price on Amazon

Try Prime Free — Free Shipping on Both Watches

The Bottom Line

The Casio F-91W and Seiko Prospex "Turtle" represent two distinct approaches to fine watchmaking — the Casio bringing Casio (Japan) tradition while Seiko delivers Made in Japan engineering.

Frequently Asked Questions

More Comparisons

Seiko Prospex Turtle vs G-Shock CasiOak

Mechanical dive heritage vs digital indestructibility

Tag Heuer Carrera Chronograph vs Casio F-91W

Tag Heuer's chronograph meets Casio's timepiece

Tag Heuer Carrera Chronograph vs Seiko Prospex "Turtle"

Tag Heuer's chronograph meets Seiko's diver

Explore These Watches

Casio F-91W — Full Review Seiko Prospex "Turtle" — Full Review Browse All Guides