Short answer

• Free tools are fine for casual users and straightforward redemptions — they cost nothing and cover most basic searches.
• Paid tools add time savings, broader partner coverage, real-time availability monitoring, advanced routing rules and alerts, and support — they’re worth it if you hunt awards often, need complex itineraries, or value faster research.
• Choose based on how often you book awards, how valuable the tickets are, and how much time you want to save.

Detailed comparison

1. Search breadth & accuracy

• Free: Airline websites, alliances’ sites, and community resources (forum posts, blogs, and some free aggregators) will find many routings but often miss partner inventory or require jumping between sites.
• Paid: Aggregators and professional tools scan many programs and partners in one place and can surface obscure partner seats that are time-consuming to find manually. They usually update frequently, but no tool is perfect — award space changes fast.

2. Speed & convenience

• Free: More manual work (multiple sites, screenshots, calling airlines). Good if you have time and like DIY.
• Paid: Faster workflows (calendar views, multi-program simultaneous searches, filters for stops/cabin/mileage), saving hours on complex searches.

3. Advanced features

• Free: Basic calendar searches, award charts on airline sites, and Google/ITA Matrix for routing inspiration.
• Paid: Multi-program search, mixed-cabin optimization, routing/rule-aware results, built-in award calculators, seat-map linking, fare class visibility, automated alerts, booking/hold assistance, and sometimes concierge booking service.

4. Alerts & monitoring

• Free: Can set manual searches or follow forum posts and Twitter feeds. Some free sites offer limited alerts.
• Paid: Automated, customizable alerts (notify when specific award inventory opens, price drops, or partner space appears). Critical for snagging hot seats.

5. Support & guarantees

• Free: Community help (forums, blogs). No official support.
• Paid: Often include email/chat support; some services offer booking help or a concierge (at extra charge). This can be valuable when complex phone bookings are required.

6. Cost vs ROI

• Free: Zero monetary cost, but higher time cost.
• Paid: Subscription or one-time fee. Typical historical ranges: low-cost tools or single searches may be inexpensive; more comprehensive services are higher. If a paid tool helps you book one high-value long-haul business/first award you wouldn’t otherwise find, it quickly pays for itself.

7. Security & privacy

• Free: Using your own account to search on airline sites is safest.
• Paid: Some tools request frequent flyer credentials or allow read-only connections to manage points. Always check security practices (OAuth vs. password storage) and whether the tool stores credentials. Prefer services that allow searches without storing passwords.

When a paid tool is worth it

• You book award travel several times per year.
• You pursue premium-cabin redemptions or complex routings (multi-carrier, stopovers, open-jaws).
• You want automated alerts so you can act fast when inventory opens.
• You sell your time (value your hours) or use awards for high-value business travel.

When stick with free tools

• You redeem points occasionally for short-haul or economy travel.
• You’re comfortable searching multiple airline sites and calling to stitch itineraries.
• You don’t need instant alerts or advanced routing help.

Practical workflow (combine both)

1. Start free: check airline and alliance sites, award charts, Google Flights/ITA for routing ideas, and forums for tips.
2. If you can’t find the seat or it’s taking too long, run a trial or single-search on a paid tool (many services offer trials or single-search purchases).
3. Use paid alerts to monitor openings; when alerted, book immediately (or have the paid/concierge service help).
4. Keep a free tracking log (or a freemium account) for balances and expiration reminders.

Checklist for choosing a paid tool

• Does it search the programs and partners you actually use?
• How often does it update availability?
• Are alerts customizable (route, cabin, program)?
• Does it require storing credentials? If so, how is data secured?
• Trial period / refund policy?
• Support quality and availability (phone/chat/email)?
• Cost structure: per-search, monthly, annual, or per-booking fee?
• User reviews / community reputation.

Common free resources to keep using

• Airline and alliance award search pages
• Airline award charts and rule pages
• Google Flights and ITA Matrix (for routing ideas)
• Forums (FlyerTalk), Reddit (/r/awardtravel), and travel blogs
• Freemium services that let you track balances or some searches

Bottom line

• Free tools work well for simple redemptions and occasional travelers. Paid tools save substantial time, unlock more partner inventory and complex routings, and provide monitoring/alerting that’s crucial for serious award hunters. If you hunt awards regularly or pursue premium cabins, a paid tool or two will likely pay for itself in saved time and better redemptions.

If you’d like, I can recommend specific paid and free tools that match common needs (e.g., best for premium cabins, best for alerts, best freemium balance tracker).