IWP vs MDY: Which ETF Is Better in 2026?
A metric-by-metric comparison of iShares Russell Mid-Cap Growth ETF (IWP) and State Street SPDR S&P MIDCAP 400 ETF Trust (MDY) — both US Mid Cap funds — using ETFValuer's daily-updated rankings.
Educational content — not financial advice. Data as of July 25, 2026. ~5 minute read.
The Verdict
IWP and MDY compete directly — both are US Mid Cap funds chasing the same job in a portfolio. That makes this a genuine either/or: the index each tracks, what it costs, and how it has handled drawdowns are what separate them, not the broad exposure they give you.
On ETFValuer's overall model — which blends return, risk-adjusted performance, cost, drawdown, size and volatility — MDY scores higher: 61.9 (Grade C) versus 44.6 for IWP. That doesn't make IWP a bad fund; it means MDY currently edges it out on this specific mix of factors. Read the metric-by-metric breakdown below before deciding which matters more for your own portfolio.
Head-to-Head: Every Metric
| IWP | MDY | |
|---|---|---|
| Category | US Mid Cap | US Mid Cap |
| Expense ratio | 0.23% | 0.23% |
| Fund size (AUM) | $21.6B | $28.1B |
| Dividend yield | 0.23% | 0.99% |
| 1-year return | -2.93% | +18.79% |
| 3-year return | +39.19% | +43.70% |
| Volatility | 17.37% | 15.64% |
| Max drawdown | -25.20% | -24.03% |
| Sharpe ratio | -0.46 | 0.88 |
| ETFValuer score | 44.6 | 61.9 |
| Grade | D | C |
| Overall rank | #398 | #210 |
Bold marks the better value in each row. "Better" is directional only (e.g. lower cost, higher return) — it isn't a recommendation by itself. See the full methodology.
Cost
On cost, the two are essentially tied — IWP charges 0.23% a year versus MDY's 0.23%. A difference this small (about $0.00 a year on a $10,000 position) isn't a reason to choose one fund over the other.
What IWP's Fees Cost You
IWP charges an expense ratio of 0.23% a year, deducted automatically from the fund's value. Small percentages compound into real money — adjust the figures below to see the impact on your own numbers.
Assumes a constant gross return and no additional contributions — a simplification, but it isolates exactly what the expense ratio costs. Try the full fee calculator to model contributions and compare any two funds.
Performance & Risk
Over the trailing 3 years, MDY returned +43.70% versus +39.19% for IWP — a gap of about 4.5 percentage points. On risk, MDY has held up better historically, with a shallower max drawdown (-24.03% vs. -25.20%). MDY currently has the better risk-adjusted return (Sharpe ratio of 0.88 vs. -0.46), meaning it delivered more return per unit of volatility taken on.
How Closely Do They Track Each Other?
Over the last 3.0 years of daily returns (752 shared trading days), IWP and MDY show a strong correlation of 0.888 — clearly related, with room to diverge. There is some genuine differentiation here, but not enough to call these complementary holdings. Pairing them mostly concentrates risk rather than spreading it.
| Measure | Value | What it means |
|---|---|---|
| Daily return correlation | 0.888 | Strong — clearly related, with room to diverge |
| R-squared | 78.9% | 78.9% of IWP's daily moves are explained by MDY's |
| Tracking error (annualised) | 9.01% | Typical yearly spread between the two funds' returns |
| Annualised return over 3.0y | IWP +11.87% · MDY +13.11% | MDY ahead by 1.24 points a year |
Correlation alone understates how far these can drift. Across every rolling 12-month window in the period, IWP finished as much as +25.9 points ahead of MDY at the best extreme and -22.8 points at the worst — a 48.7-point spread between the best and worst year of relative performance. Two funds can correlate tightly day to day and still deliver very different outcomes over any single year you happen to hold them.
Calculated from daily total returns over the trailing 3-year window, recomputed every day this site refreshes. Correlation of 1.00 means the two funds moved in lockstep; 0.00 means their daily moves were unrelated.
Which One Should You Pick?
Lean IWP if…
- You prefer to keep holdings under one roof at iShares
Lean MDY if…
- Current income matters to you — it yields 0.99% against 0.23%
- You care about return per unit of risk — its Sharpe ratio of 0.88 beats -0.46
- You weight recent results heavily — it returned 43.7% over 3 years against 39.2%
Whichever you pick, holding both at full weight is usually the wrong answer — see the overlap and correlation sections above.
Frequently Asked Questions
Is IWP or MDY better?
On ETFValuer's overall model — which blends return, risk-adjusted performance, cost, drawdown, size and volatility — MDY scores higher: 61.9 (Grade C) versus 44.6 for IWP. That doesn't make IWP a bad fund; it means MDY currently edges it out on this specific mix of factors. Read the metric-by-metric breakdown below before deciding which matters more for your own portfolio.
Which has the lower expense ratio, IWP or MDY?
MDY currently has the lower expense ratio (0.23% vs. 0.23%).
Can I hold both IWP and MDY?
You can, though the benefit is limited. At a correlation of 0.89, IWP and MDY fall together far more often than not, so owning both adds complexity and a second expense ratio without much real diversification. Most investors are better served picking one.
Go deeper on either fund
Full daily-updated metrics, holdings context, and category peers.