Is it better to maximize memory usage or number of passes with Argon2i 1.3?
As of October 2017, the resource I've found most useful for getting a quick, practical sense of how pick parameters for Argon2 is the (still draft) RFC, in particular section 9, which gives this guidance (in 9.2):

The best attacks on the 1-pass and 2-pass Argon2i is the low-storage attack described in [CBS16], which reduces the time-area product (using the peak memory value) by the factor of 5.  The best attack on 3-pass and more Argon2i is [AB16] with reduction factor being a function of memory size and the number of passes. For 1 gibibyte of memory: 3 for 3 passes, 2.5 for 4 passes, 2 for 6 passes. The reduction factor grows by about 0.5 with every doubling the memory size. To completely prevent time-space tradeoffs from [AB16], the number of passes must exceed binary logarithm of memory minus 26.

Since $\log_2(128\ \mathrm{MiB}) = 27$, this actually suggests that you should be able to use $t = 3$, $m = 128\ \mathrm{MiB}$ as your first alternative proposes.  (Yes, $27 - 26 = 1$, but you need at least three passes to defeat the [CBS16] attacks.)
It's also worth quoting section 9.3 in full:

9.3. Security for time-bounded defenders
A bottleneck in a system employing the password-hashing function is often the function latency rather than memory costs. A rational defender would then maximize the bruteforce costs for the attacker equipped with a list of hashes, salts, and timing information, for fixed computing time on the defender’s machine. The attack cost estimates from [AB16] imply that for Argon2i, 3 passes is almost optimal for the most of reasonable memory sizes, and that for Argon2d and Argon2id, 1 pass maximizes the attack costs for the constant defender time.

The draft RFC doesn't say which memory sizes they consider reasonable, but they do repeatedly use 1 GiB throughout the draft as a reference figure.  For example the reduction factors given in the first quote are based on 1 GiB, and the quote notes that these increase with more memory—but you're proposing to use less memory than that.

Or, as your question proposes and comments concur, you might consider not using Argon2i.  The draft RFC in fact recommends Argon2id over either 2i or 2d.  Then you just need one pass, because the advantage of tradeoff attacks on 2d and 2id doesn't depend on the number of passes (section 9.2):

The best tradeoff attack on $t$-pass Argon2d is the ranking tradeoff attack, which reduces the time-area product by the factor of 1.33.
The best attack on Argon2id can be obtained by complementing the best attack on the 1-pass Argon2i with the best attack on a multi-pass Argon2d. Thus The best tradeoff attack on 1-pass Argon2id is the combined low-storage attack (for the first half of the memory) and the ranking attack (for the second half), which bring together the factor of about 2.1. The best tradeoff attack on t-pass Argon2id is the ranking tradeoff attack, which reduces the time-area product by the factor of 1.33.

So for 1 GiB memory size, you need six passes of Argon2i to reduce attacker advantage to a similar level as one-pass Argon2id (2 vs. 2.1), and both are still behind Argon2d (1.33).  This speaks strongly in favor of Argon2id, and is presumably the reason the draft RFC recommends it.