Compare Products: The Niacinamide 15 Serum vs C15 Super Booster

COSRX

The Niacinamide 15 Serum

Mid-range15%
$25 / 20ml — $1.25/ml
Paula's Choice

C15 Super Booster

Premium
$55 / 20ml — $2.75/ml

Who It's Designed For

COSRX
  • Oily and acne-prone skin seeking serious oil control
  • Post-acne marks and hyperpigmentation
  • Enlarged pores and textured skin
  • Users ready to step up from 10% to higher-strength niacinamide
  • Those who prefer minimal-ingredient formulas
Paula's Choice
  • Those seeking a CE Ferulic serum with added peptide benefits
  • Users who want collagen stimulation from both vitamin C and peptides
  • People who prefer mixing a vitamin C booster into their existing products
  • Prestige skincare shoppers who want the formula at Sephora
  • Users comfortable with 15% L-ascorbic acid concentration

Key Ingredients

COSRX

Niacinamide (15%), Acetyl Glucosamine (2%), Zinc PCA (1%), Allantoin (0.1%)

Paula's Choice

15% L-Ascorbic Acid, Ferulic Acid, Tocopherol (Vitamin E), Peptides (Tridecapeptide-1, Palmitoyl Tripeptide-5), Sodium Hyaluronate

Product Composition

27% similarity (8 ingredients in common)

Shared Ingredients
waterpentylene glycol12-hexanediolethylhexylglycerinsodium phytatecitric acidtocopherol
Only in COSRX (8)
niacinamidebutylene glycolacetyl glucosaminezinc pcatrehalosexanthan gumpullulanallantoin
Only in Paula's Choice (14)
ascorbic acidethoxydiglycolppg-26-buteth-26mannitolpalmitoyl tripeptide-5peg-40 hydrogenated castor oilbisabololdecylene glycolferulic acidoryza sativa (rice) bran extractpolyacrylate crosspolymer-6panthenolergothioneinephenoxyethanol

User Feedback Patterns

COSRX
Oil control standout

Users consistently report significant reduction in daytime oil and shine. Many describe it as the best niacinamide serum they have tried for sebum control.

Lightweight texture praised

Unlike some high-concentration serums, this absorbs quickly without tackiness or residue. Layers well under other products.

Small bottle concern

The 20ml size (vs. 30ml standard) is a common gripe, especially given the price point.

Pore improvement takes time

Users report visible pore improvement around the 3-4 week mark with consistent twice-daily use.

Paula's Choice
Noticeable brightening

Users consistently report visible brightening and improved skin tone within 2-4 weeks. The 15% concentration is effective for most users.

Expensive per ml

At $55 for 20ml, this is one of the priciest vitamin C serums relative to volume. Users note the small bottle size is a drawback for daily full-face use.

Freshness concerns

Multiple reviewers report receiving bottles that appear already oxidized (yellow or orange). This is a recurring complaint that the brand has acknowledged.

Mixes well with other products

The booster format is praised for flexibility. Users mix it with moisturizer, sunscreen, or other serums without issues.

Which Should You Buy?

COSRX The Niacinamide 15 Serum offers great value at a lower price point. Paula's Choice C15 Super Booster may be worth the premium if you want 15% L-Ascorbic Acid.

View Full Product Details

Related Comparisons